Douglas Funk - Academia.edu (original) (raw)

Papers by Douglas Funk

Research paper thumbnail of Effects of opioid receptor blockade on the renewal of alcohol seeking induced by context : relationship to c-fos mRNA expression

European Journal of Neuroscience, 2007

Contextual stimuli associated with alcohol availability can induce alcohol seeking during abstine... more Contextual stimuli associated with alcohol availability can induce alcohol seeking during abstinence. Using a renewal procedure, we tested the effect of opioid receptor blockade on context-induced alcohol seeking, and its relationship to the activity of brain sites involved in learning and reward. Thirty-six male Wistar rats were trained to lever press for a 12% (w ⁄ v) alcohol solution before undergoing extinction sessions (no alcohol delivery). Half of the rats underwent training, extinction and testing in a single context with a distinct set of olfactory, visual, auditory and tactile properties [training, extinction and test in Context A (AAA)]. The other half were trained and extinguished in different contexts and returned to the training context on the test day [training, extinction and test in Contexts A, B and A, respectively (ABA)]. On the test day, the rats from each condition were pre-treated with either saline or 1 mg ⁄ kg naltrexone (s.c.) and tested for alcohol seeking. Immediately following the test session, rats were killed and their brains were analysed for c-fos mRNA expression using in-situ hybridization. Re-exposure to the alcohol-associated context (ABA) significantly increased operant behaviour on the previously active lever relative to the AAA groups and this increased responding was associated with increased c-fos mRNA expression in the basal and lateral amygdala and the CA3 subregion of the hippocampus. Naltrexone pretreatment attenuated context-induced alcohol seeking and inhibited c-fos mRNA expression in the lateral amygdala and CA3. Our findings point to a critical role for the basolateral amygdala and dorsal hippocampus in mediating context-induced renewal of alcohol seeking and suggest that opioidergic mechanisms mediate this effect.

Research paper thumbnail of Biological Processes Underlying Co-Use of Alcohol and Nicotine: Neuronal Mechanisms, Cross-Tolerance, and Genetic Factors

Alcohol Research Health the Journal of the National Institute on Alcohol Abuse and Alcoholism, Feb 1, 2006

tobacco; alcohol and other drug (AOD) use, abuse, and dependence; nicotine dependence; dual addic... more tobacco; alcohol and other drug (AOD) use, abuse, and dependence; nicotine dependence; dual addiction; brain; ventral tegmental area; mesolimbic dopamine system; animal models; genetic theory of alcohol and other drug use (AODU); cross-tolerance tine

Research paper thumbnail of Periadolescent and adult rats respond differently in tests measuring the rewarding and aversive effects of nicotine

Psychopharmacologia, Apr 4, 2006

Rationale: Initiation of tobacco use typically begins during adolescence, and the nature of these... more Rationale: Initiation of tobacco use typically begins during adolescence, and the nature of these first experiences with nicotine may affect the probability of continued use. In rodents, a number of studies suggest that periadolescents are more responsive to the rewarding effects of nicotine compared to adults. Objectives: This study was designed to determine if there are age differences in the rewarding and aversive effects of nicotine by using the conditioned place preference (CPP) and conditioned taste avoidance (CTA) paradigms, respectively. We also examined age differences in locomotor responses to nicotine. Methods: In the CPP paradigm, male periadolescent and adult Wistar rats received nicotine (0.2, 0.4, or 0.8 mg/kg, s.c.) or vehicle prior to place conditioning trials. In the CTA paradigm, in separate groups of rats, periadolescents and adults were exposed to a 0.1% saccharin solution, followed by the administration of nicotine (0.2, 0.4, or 0.8 mg/kg, s.c.) or vehicle. Four saccharinnicotine pairings were followed by a preference test and three extinction sessions. Results: In the CPP paradigm, nicotine produced a dose-dependent place preference in periadolescent, but not in adult, rats. In the CTA paradigm, adult rats expressed a dose-dependent avoidance of saccharin after pairings with nicotine, whereas periadolescents were resistant to CTA formation. With regard to locomotor activity, adults and periadolescents showed comparable locomotor responses to nicotine.

Research paper thumbnail of Effect of prazosin and guanfacine on stress-induced reinstatement of food and alcohol seeking in rats

Appetite, 2011

Relapse to alcohol use during abstinence or maladaptive eating habits during dieting is often pro... more Relapse to alcohol use during abstinence or maladaptive eating habits during dieting is often provoked by stress. The anxiogenic drug yohimbine, a prototypical ␣-2 adrenoceptor antagonist, which causes stress-like responses in humans and non-humans, reliably reinstates alcohol and food seeking in a rat relapse model. Here, we studied the effect of the ␣-1 adrenoceptor antagonist prazosin and the ␣-2 adrenoceptor agonist guanfacine on yohimbine-induced reinstatement. In Exp. 1, we trained rats to self-administer alcohol, and after extinction of alcohol-reinforced lever pressing, we tested prazosin's or guanfacine's effect on yohimbine-induced reinstatement; we also examined prazosin's effect on footshockstress-induced reinstatement. In Exp. 2, we trained food-restricted rats to self-administer food pellets and first examined prazosin's or guanfacine's effects on food-reinforced responding, and then, after extinction of lever presses, on yohimbine-induced reinstatement. Prazosin blocked yohimbine-induced reinstatement of food and alcohol seeking, as well as footshock-induced reinstatement of alcohol seeking. Guanfacine attenuated yohimbine-induced reinstatement of alcohol seeking at the highest dose, but its effect on yohimbine-induced reinstatement of food seeking was not significant. Neither prazosin nor guanfacine affected high-rate food-reinforced responding. Results demonstrate an important role of postsynaptic ␣-1 adrenoceptors in stress-induced reinstatement of alcohol and food seeking.

Research paper thumbnail of Stress-Induced Reinstatement of Drug Seeking: 20 Years of Progress

Neuropsychopharmacology, 2015

In human addicts, drug relapse and craving are often provoked by stress. Since 1995, this clinica... more In human addicts, drug relapse and craving are often provoked by stress. Since 1995, this clinical scenario has been studied using a rat model of stress-induced reinstatement of drug seeking. Here, we first discuss the generality of stress-induced reinstatement to different drugs of abuse, different stressors, and different behavioral procedures. We also discuss neuropharmacological mechanisms, and brain areas and circuits controlling stress-induced reinstatement of drug seeking. We conclude by discussing results from translational human laboratory studies and clinical trials that were inspired by results from rat studies on stress-induced reinstatement. Our main conclusions are: (1) The phenomenon of stress-induced reinstatement, first shown with an intermittent footshock stressor in rats trained to self-administer heroin, generalizes to other abused drugs, including cocaine, methamphetamine, nicotine, and alcohol, and is also observed in the conditioned place preference model in rats and mice. This phenomenon, however, is stressor-specific and not all stressors induce reinstatement of drug seeking. (2) Neuropharmacological studies indicate the involvement of corticotropin-releasing factor (CRF), noradrenaline, dopamine, glutamate, kappa/dynorphin, and several other peptide and neurotransmitter systems in stress-induced reinstatement. Neuropharmacology and circuitry studies indicate the involvement of CRF and noradrenaline transmission in bed nucleus of stria terminalis and central amygdala, and dopamine, CRF, kappa/dynorphin, and glutamate transmission in other components of the mesocorticolimbic dopamine system (ventral tegmental area, medial prefrontal cortex, orbitofrontal cortex, and nucleus accumbens). (3) Translational human laboratory studies and a recent clinical trial study show the efficacy of alpha-2 adrenoceptor agonists in decreasing stress-induced drug craving and stress-induced initial heroin lapse.Neuropsychopharmacology accepted article preview online, 15 May 2015. doi:10.1038/npp.2015.142.

Research paper thumbnail of Effects of pharmacological stressors on c-fos and CRF mRNA in mouse brain: Relationship to alcohol seeking

Neuroscience Letters, Sep 1, 2008

A marked heterogeneity exists among stressors in their ability to reinstate alcohol seeking in ra... more A marked heterogeneity exists among stressors in their ability to reinstate alcohol seeking in rats. We have reported that the pharmacological stressor yohimbine, an alpha-2 adrenoceptor antagonist, potently reinstated alcohol seeking, but FG-7142, a benzodiazepine inverse agonist was ineffective. In rats, we determined that yohimbine elicits patterns of brain expression of the mRNAs for c-fos, a marker of neuronal activation, and corticotropin-releasing factor (CRF) a stress-related peptide, distinct from that produced by FG-7142. The purpose of the present experiment is to determine if these differential effects of yohimbine and FG-7142 on regional c-fos and CRF mRNA expression generalize to another animal commonly used in alcohol research, the C57 BL/6J mouse. In comparing the results of the present study to those of our previous one, we found a number of commonalities in the patterns of activation elicited by yohimbine and FG-7142 between the two species, and some notable differences. As we found in the rat, yohimbine selectively increased c-fos mRNA in the mouse NACs, BLA and CeA. Yohimbine increased CRF mRNA only in the mouse PVN, but was without effect on CRF mRNA in extrahypothalamic sites, the BNST and CeA. This differs from what we saw in the rat, where yohimbine increased CRF mRNA in these extrahypothalamic regions, but not the PVN. The selective induction of c-fos in the NACs, BLA and CeA of mice and rats by yohimbine offers further support for the idea that activation of these structures participates in reinstatement induced by such stressors.

Research paper thumbnail of The CRF 1 receptor antagonist antalarmin attenuates yohimbine-induced increases in operant alcohol self-administration and reinstatement of alcohol seeking in rats

Psychopharmacology, 2007

Yohimbine is an alpha-2 adrenoreceptor antagonist that provokes stress- and anxiety-like response... more Yohimbine is an alpha-2 adrenoreceptor antagonist that provokes stress- and anxiety-like responses in both humans and laboratory animals. In rats, yohimbine increases operant alcohol self-administration and reinstates alcohol seeking. In this study, we assess whether these effects of yohimbine are attenuated by systemic injections of the corticotrotropin-releasing factor 1 (CRF1) receptor antagonist antalarmin. In Exp. 1, we trained rats to lever press for alcohol solutions (12% w/v, 1 h/day) over several weeks; during training, the response requirement was increased from a fixed-ratio-1 (FR-1) to a fixed-ratio-3 (FR-3) reinforcement schedule. We then tested the effect of antalarmin (10 or 20 mg/kg) on yohimbine (1.25 mg/kg)-induced increases in operant alcohol self-administration (FR-3 reinforcement schedule). Subsequently, we assessed the effect of antalarmin on yohimbine-induced increases in plasma corticosterone levels in the previously self-administering rats. In Exp. 2, we trained the rats to self-administer alcohol as in Exp. 1, and after extinction of the alcohol-reinforced lever responding over 13 days, we tested antalarmin's effect on yohimbine-induced reinstatement of alcohol seeking. Yohimbine increased operant alcohol self-administration and reinstated alcohol seeking after extinction. These effects of yohimbine were attenuated by antalarmin. Antalarmin injections in the absence of yohimbine had no effect on either operant alcohol self-administration or extinction responding. Antalarmin had no effect on yohimbine-induced corticosterone release in alcohol-experienced rats. These results suggest that extrahypothalamic CRF1 receptors are involved in the effect of yohimbine on operant alcohol self-administration and on relapse to alcohol seeking and support the notion that CRF1 receptor antagonists should be considered in alcohol addiction treatment.

Research paper thumbnail of IncreasedVulnerabilitytoNicotineSelf-Administrationand RelapseinAlcohol-NaiveOffspringofRatsSelectivelyBred forHighAlcoholIntake

The prevalence of smoking in human alcoholics is substantially higher than in the general populat... more The prevalence of smoking in human alcoholics is substantially higher than in the general population, and results from twin studies suggest that a shared genetic vulnerability underlies alcohol and nicotine addiction. Here, we directly tested this hypothesis by examining nicotine-taking behavior in alcohol-naive offspring of alcohol-preferring (P) rats and alcohol-nonpreferring (NP) rats that had been selectively bred for high and low alcohol intake. The self-administration of intravenous nicotine (0.015-0.060 mg/kg per infusion) in P rats was more than twice than that of NP rats. Nicotine seeking induced by reexposure to nicotine cues in extinction tests was also substantially greater in P rats than in NP rats. In a subsequent relapse test, priming nicotine injections reinstated drug seeking in P rats but not NP rats. P rats also self-administered higher amounts of oral sucrose (1-20%) than NP rats, a finding consistent with previous reports. In contrast, self-administration of intravenous cocaine (0.1875-1.125 mg/kg per infusion) was remarkably similar in the P and NP rats; however, P-NP differences in cocaine seeking emerged in subsequent extinction and cocaine priming-induced reinstatement tests. In both cases, lever responding was higher in P rats than in NP rats. Thus, alcohol-naive offspring of rats genetically selected for high alcohol intake are highly susceptible to nicotine self-administration and relapse, and this susceptibility is not likely caused by general reward deficits in NP rats. The present findings provide experimental evidence for the hypothesis that a shared genetic determinant accounts for the co-abuse of nicotine and alcohol.

Research paper thumbnail of Shaham Y, Funk D, Erb S, Brown TJ, Walker CD, Stewart J. Corticotropin-releasing factor, but not corticosterone, is involved in stress-induced relapse to heroin-seeking in rats. J Neurosci 17: 2605-2614

The Journal of Neuroscience : The Official Journal of the Society for Neuroscience

We showed previously that brief footshock stress and priming injections of heroin reinstate heroi... more We showed previously that brief footshock stress and priming injections of heroin reinstate heroin-seeking after prolonged drug-free periods. Here, we examined whether the adrenal hormone, corticosterone, and brain corticotropin-releasing factor (CRF) were involved in such reinstatement. We tested the effects of adrenalectomy, chronic exposure to the corticosterone synthesis inhibitor metyrapone (100 mg/kg, s.c., twice daily), acute exposure to metyrapone, acute intracerebroventricular injections of CRF (0.3 and 1.0 g), and intracerebroventricular injections of the CRF antagonist ␣-helical CRF (3 and 10 g). Rats were trained to self-administer heroin (100 g/kg/ infusion, i.v.) for 12-14 d. Extinction sessions were given for 4 -8 d (saline substituted for heroin). Tests for reinstatement were given after priming injections of saline and of heroin (0.25 mg/kg, s.c.), and after intermittent footshock (15 or 30 min, 0.5 mA). Adrenalectomy (performed after training) did not affect reinstatement by heroin but appeared to potentiate the reinstatement by footshock. Chronic exposure to metyrapone (from the beginning of extinction) or an acute injection of metyrapone (3 hr before testing) did not alter the reinstatement of heroinseeking induced by footshock or heroin. Acute exposure to metyrapone alone potently reinstated heroin-seeking. In addition, acute exposure to CRF reinstated heroin-seeking, and the CRF antagonist ␣-helical CRF attenuated stress-induced relapse. The effect of the CRF antagonist on reinstatement by heroin was less consistent. These results suggest that CRF, a major brain peptide involved in stress, contributes to relapse to heroin-seeking induced by stressors.

Research paper thumbnail of Stress- and pellet-priming-induced reinstatement of food seeking and neuronal activation in c-fos-GFP transgenic female rats. Role of ovarian hormones

Appetite, 2011

Relapse to alcohol use during abstinence or maladaptive eating habits during dieting is often pro... more Relapse to alcohol use during abstinence or maladaptive eating habits during dieting is often provoked by stress. The anxiogenic drug yohimbine, a prototypical ␣-2 adrenoceptor antagonist, which causes stress-like responses in humans and non-humans, reliably reinstates alcohol and food seeking in a rat relapse model. Here, we studied the effect of the ␣-1 adrenoceptor antagonist prazosin and the ␣-2 adrenoceptor agonist guanfacine on yohimbine-induced reinstatement. In Exp. 1, we trained rats to self-administer alcohol, and after extinction of alcohol-reinforced lever pressing, we tested prazosin's or guanfacine's effect on yohimbine-induced reinstatement; we also examined prazosin's effect on footshockstress-induced reinstatement. In Exp. 2, we trained food-restricted rats to self-administer food pellets and first examined prazosin's or guanfacine's effects on food-reinforced responding, and then, after extinction of lever presses, on yohimbine-induced reinstatement. Prazosin blocked yohimbine-induced reinstatement of food and alcohol seeking, as well as footshock-induced reinstatement of alcohol seeking. Guanfacine attenuated yohimbine-induced reinstatement of alcohol seeking at the highest dose, but its effect on yohimbine-induced reinstatement of food seeking was not significant. Neither prazosin nor guanfacine affected high-rate food-reinforced responding. Results demonstrate an important role of postsynaptic ␣-1 adrenoceptors in stress-induced reinstatement of alcohol and food seeking.

Research paper thumbnail of Effect of prazosin and guanfacine on stress-induced reinstatement of alcohol and food seeking in rats

Psychopharmacology, 2011

Rationale and Objectives-Relapse to alcohol use during abstinence or maladaptive eating habits du... more Rationale and Objectives-Relapse to alcohol use during abstinence or maladaptive eating habits during dieting is often provoked by stress. The anxiogenic drug yohimbine, which causes stress-like responses in humans and nonhumans, reliably reinstates alcohol and food seeking in a rat relapse model. Yohimibine is a prototypical alpha-2 adrenoceptor antagonist but results from studies on noradrenaline's role in yohimbine-induced reinstatement of drug and food seeking are inconclusive. Here we further addressed this issue by studying the effect of the alpha-1 adrenoceptor antagonist prazosin and the alpha-2 adrenoceptor agonist guanfacine on yohimbineinduced reinstatement.

Research paper thumbnail of Stress-Induced Reinstatement of Drug Seeking: 20 Years of Progress

Neuropsychopharmacology : official publication of the American College of Neuropsychopharmacology, Jan 15, 2015

In human addicts, drug relapse and craving are often provoked by stress. Since 1995, this clinica... more In human addicts, drug relapse and craving are often provoked by stress. Since 1995, this clinical scenario has been studied using a rat model of stress-induced reinstatement of drug seeking. Here, we first discuss the generality of stress-induced reinstatement to different drugs of abuse, different stressors, and different behavioral procedures. We also discuss neuropharmacological mechanisms, and brain areas and circuits controlling stress-induced reinstatement of drug seeking. We conclude by discussing results from translational human laboratory studies and clinical trials that were inspired by results from rat studies on stress-induced reinstatement. Our main conclusions are: (1) The phenomenon of stress-induced reinstatement, first shown with an intermittent footshock stressor in rats trained to self-administer heroin, generalizes to other abused drugs, including cocaine, methamphetamine, nicotine, and alcohol, and is also observed in the conditioned place preference model in r...

Research paper thumbnail of Corticotropin-releasing factor, but not corticosterone, is involved in stress-induced relapse to heroin-seeking in rats

The Journal of neuroscience : the official journal of the Society for Neuroscience, 1997

We showed previously that brief footshock stress and priming injections of heroin reinstate heroi... more We showed previously that brief footshock stress and priming injections of heroin reinstate heroin-seeking after prolonged drug-free periods. Here, we examined whether the adrenal hormone, corticosterone, and brain corticotropin-releasing factor (CRF) were involved in such reinstatement. We tested the effects of adrenalectomy, chronic exposure to the corticosterone synthesis inhibitor metyrapone (100 mg/kg, s.c., twice daily), acute exposure to metyrapone, acute intracerebroventricular injections of CRF (0.3 and 1.0 microgram), and intracerebroventricular injections of the CRF antagonist alpha-helical CRF (3 and 10 micrograms). Rats were trained to self-administer heroin (100 micrograms/kg/infusion, i.v.) for 12-14 d. Extinction sessions were given for 4-8 d (saline substituted for heroin). Tests for reinstatement were given after priming injections of saline and of heroin (0.25 mg/kg, s.c.), and after intermittent footshock (15 or 30 min, 0.5 mA). Adrenalectomy (performed after tra...

Research paper thumbnail of Effects of injections of 8-hydroxy-2-(di-n-propylamino)tetralin or muscimol in the median raphe nucleus on c-fos mRNA in the rat brain

Neuroscience, 2005

Inhibition of the median raphe nucleus (MRN) by the local injection of 5-HT(1A) or GABA(A) recept... more Inhibition of the median raphe nucleus (MRN) by the local injection of 5-HT(1A) or GABA(A) receptor agonists produces strong activational effects on feeding, drinking and locomotor activity. Using an animal model of relapse, we have shown that intra-MRN injection of the 5-HT(1A) autoreceptor agonist 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT) reinstates alcohol seeking in rats. The circuitry underlying the behavioral effects of intra-MRN injection of these drugs is not known. In order to identify the brain areas that may be involved, we measured levels of mRNA of the immediate early gene c-fos in discrete nuclei of the rat brain following intra-MRN infusions of these drugs. Male Wistar rats received intra-MRN infusions of 8-OH-DPAT (1 mug), muscimol (25 ng) or saline vehicle immediately prior to placement in locomotor activity chambers. Thirty minutes later, they were decapitated, and their brains processed for in situ hybridization of c-fos mRNA. In agreement with previous r...

Research paper thumbnail of Effect of blockade of corticotropin-releasing factor receptors in the median raphe nucleus on stress-induced c-fos mRNA in the rat brain

Neuroscience, 2003

Using a rat relapse model, we have shown that infusion of a corticotropin-releasing factor (CRF) ... more Using a rat relapse model, we have shown that infusion of a corticotropin-releasing factor (CRF) receptor antagonist into the median raphe nucleus (MRN) blocks footshock stress-induced reinstatement of alcohol seeking in rats. The goal of the present study was to begin identifying brain sites potentially involved in this effect. For this purpose, we measured levels of c-fos mRNA in discrete nuclei of the rat brain following exposure to intermittent footshock, which was preceded by intra-MRN infusions of a CRF receptor antagonist, d-Phe CRF (0 or 50 ng). Exposure to intermittent footshock increased the expression of c-fos mRNA in a number of brain regions previously shown to be responsive to stressful stimuli. Pretreatment with d-Phe CRF in the MRN selectively attenuated the increases in c-fos mRNA induced by footshock in the central nucleus of the amygdala (CeA). These findings are consistent with previous data on the important role for the CeA in stress-induced reinstatement of dru...

Research paper thumbnail of The role of kappa opioid receptors in stress-induced reinstatement of alcohol seeking in rats

Brain and Behavior, 2014

Introduction: Stress is related to heavy alcohol use and relapse in alcoholics. Using the reinsta... more Introduction: Stress is related to heavy alcohol use and relapse in alcoholics. Using the reinstatement model, we have shown that corticotropin-releasing factor (CRF) underlies stress-induced relapse to alcohol seeking in laboratory rodents. Little is known about how other neurotransmitters interact with CRF in these effects. Dynorphin and its receptor (kappa opioid receptor, KOR) are involved in stress responses and in alcohol seeking. KOR and CRF receptors (CRF R) may interact in the production of stress-related behaviors but it is not known whether this interaction is involved in reinstatement of alcohol seeking. Methods: Male Long Evans rats were trained to self-administer alcohol (12% w/v). After extinction of responding, we determined the effects of the KOR agonist, U50,488 (2.5, 5 mg/kg) on reinstatement of alcohol seeking, and their sensitivity to the selective KOR antagonist nor-binaltorphimine dihydrochloride (nor-BNI) (10 mg/kg) administered at different times before U50,488. We then examined the effects of nor-BNI on reinstatement induced by the stressor yohimbine (1.25 mg/kg) and on reinstatement induced by exposure to alcoholassociated cues . Finally, we determined whether CRF R1 blockade with antalarmin (10, 20 mg/kg) attenuates alcohol seeking induced by U50,488. Results: U50,488 reinstated alcohol seeking. Prior treatment with nor-BNI 2, but not 24 h before administration of U50,488 or yohimbine blocked reinstatement induced by these drugs. Cue-induced reinstatement was blocked by nor-BNI administered 2 h prior to testing. Finally, U50,488-induced reinstatement was blocked by antalarmin. Conclusions: These data further support a role for KOR in reinstatement of alcohol seeking under nonstress and stressful conditions and that KOR and CRF R interact in these effects.

Research paper thumbnail of The CRF1 receptor antagonist antalarmin attenuates yohimbine-induced increases in operant alcohol self-administration and reinstatement of alcohol seeking in rats

Psychopharmacology, 2007

Yohimbine is an alpha-2 adrenoreceptor antagonist that provokes stress- and anxiety-like response... more Yohimbine is an alpha-2 adrenoreceptor antagonist that provokes stress- and anxiety-like responses in both humans and laboratory animals. In rats, yohimbine increases operant alcohol self-administration and reinstates alcohol seeking. In this study, we assess whether these effects of yohimbine are attenuated by systemic injections of the corticotrotropin-releasing factor 1 (CRF1) receptor antagonist antalarmin. In Exp. 1, we trained rats to lever press for alcohol solutions (12% w/v, 1 h/day) over several weeks; during training, the response requirement was increased from a fixed-ratio-1 (FR-1) to a fixed-ratio-3 (FR-3) reinforcement schedule. We then tested the effect of antalarmin (10 or 20 mg/kg) on yohimbine (1.25 mg/kg)-induced increases in operant alcohol self-administration (FR-3 reinforcement schedule). Subsequently, we assessed the effect of antalarmin on yohimbine-induced increases in plasma corticosterone levels in the previously self-administering rats. In Exp. 2, we trained the rats to self-administer alcohol as in Exp. 1, and after extinction of the alcohol-reinforced lever responding over 13 days, we tested antalarmin's effect on yohimbine-induced reinstatement of alcohol seeking. Yohimbine increased operant alcohol self-administration and reinstated alcohol seeking after extinction. These effects of yohimbine were attenuated by antalarmin. Antalarmin injections in the absence of yohimbine had no effect on either operant alcohol self-administration or extinction responding. Antalarmin had no effect on yohimbine-induced corticosterone release in alcohol-experienced rats. These results suggest that extrahypothalamic CRF1 receptors are involved in the effect of yohimbine on operant alcohol self-administration and on relapse to alcohol seeking and support the notion that CRF1 receptor antagonists should be considered in alcohol addiction treatment.

Research paper thumbnail of Blunted cortisol rhythm is associated with learning impairment in aged hamsters

Physiology & behavior, Jan 15, 2004

In mammals, the cognitive decline that accompanies unsuccessful aging is associated with circadia... more In mammals, the cognitive decline that accompanies unsuccessful aging is associated with circadian rhythm dysfunction and increased levels of circulating glucocorticoids. The possible causal relations among these factors are not known. To test for primary effects of circadian clock dysfunction versus increased glucocorticoid levels as contributors to age-related learning impairment, we measured cortisol and wheel-running rhythms along with context learning in aged hamsters (15-18 months). At this age, locomotor rhythms of learners and nonlearners were found to be indistinguishable. However, plasma cortisol levels were lower, and the amplitude of the cortisol rhythm was reduced in the impaired animals. These data suggest that age-related cognitive decline may be related more to a loss of hormone rhythmicity than to a loss of behavioral rhythmicity or an increase in hormone level.

Research paper thumbnail of Biological processes underlying co-use of alcohol and nicotine: neuronal mechanisms, cross-tolerance, and genetic factors

Alcohol research & health : the journal of the National Institute on Alcohol Abuse and Alcoholism, 2006

Alcohol and nicotine are two of the oldest and most commonly used recreational drugs, and many pe... more Alcohol and nicotine are two of the oldest and most commonly used recreational drugs, and many people use both of them together. Although their ready availability likely contributes to the strong correlation between alcohol and nicotine use, several lines of evidence suggest that biological factors play a role as well. For example, both alcohol and nicotine act on a brain system called the mesolimbic dopamine system, which mediates the rewarding and reinforcing properties of both drugs. Modification of the activities of the mesolimbic dopamine system can interfere with the effects of both alcohol and nicotine. Another mechanism that may contribute to alcohol-nicotine interactions is cross-tolerance to the effects of both drugs. Finally, genetic studies in humans and of selectively bred mouse and rat strains suggest that shared genetic factors help determine a person's liability to use or abuse both alcohol and nicotine.

Research paper thumbnail of Intra-median raphe nucleus (MRN) infusions of muscimol, a GABA-A receptor agonist, reinstate alcohol seeking in rats: role of impulsivity and reward

Psychopharmacology, 2008

We previously found that the inhibition of median raphe nucleus (MRN) 5-HT transmission by local ... more We previously found that the inhibition of median raphe nucleus (MRN) 5-HT transmission by local injections of a 5-HT1A agonist 8-OH-DPAT or corticotrophin-releasing factor (CRF) mimic the effect of foot shock stress to reinstate alcohol seeking. In this study, we further explored the role of the MRN by examining the effect of inhibition of MRN neurons, by injecting the GABA-A receptor agonist muscimol, on the reinstatement of alcohol seeking. Male rats were trained to lever press for 12% alcohol. Cannulae were implanted aimed at the MRN; some rats were also given intra-MRN injections of 5,7-DHT to destroy ascending 5-HT neurons. After retraining, alcohol responding was extinguished for 14 days. Subsequently, we tested the effect of muscimol injections into the MRN (0, 12.5, 25, 50 ng) on reinstatement. We also tested the effect of MRN muscimol injections on a measure of reward, conditioned place preference (CPP) and performance in the five-choice serial reaction time task (5-CSRTT)...

Research paper thumbnail of Effects of opioid receptor blockade on the renewal of alcohol seeking induced by context : relationship to c-fos mRNA expression

European Journal of Neuroscience, 2007

Contextual stimuli associated with alcohol availability can induce alcohol seeking during abstine... more Contextual stimuli associated with alcohol availability can induce alcohol seeking during abstinence. Using a renewal procedure, we tested the effect of opioid receptor blockade on context-induced alcohol seeking, and its relationship to the activity of brain sites involved in learning and reward. Thirty-six male Wistar rats were trained to lever press for a 12% (w ⁄ v) alcohol solution before undergoing extinction sessions (no alcohol delivery). Half of the rats underwent training, extinction and testing in a single context with a distinct set of olfactory, visual, auditory and tactile properties [training, extinction and test in Context A (AAA)]. The other half were trained and extinguished in different contexts and returned to the training context on the test day [training, extinction and test in Contexts A, B and A, respectively (ABA)]. On the test day, the rats from each condition were pre-treated with either saline or 1 mg ⁄ kg naltrexone (s.c.) and tested for alcohol seeking. Immediately following the test session, rats were killed and their brains were analysed for c-fos mRNA expression using in-situ hybridization. Re-exposure to the alcohol-associated context (ABA) significantly increased operant behaviour on the previously active lever relative to the AAA groups and this increased responding was associated with increased c-fos mRNA expression in the basal and lateral amygdala and the CA3 subregion of the hippocampus. Naltrexone pretreatment attenuated context-induced alcohol seeking and inhibited c-fos mRNA expression in the lateral amygdala and CA3. Our findings point to a critical role for the basolateral amygdala and dorsal hippocampus in mediating context-induced renewal of alcohol seeking and suggest that opioidergic mechanisms mediate this effect.

Research paper thumbnail of Biological Processes Underlying Co-Use of Alcohol and Nicotine: Neuronal Mechanisms, Cross-Tolerance, and Genetic Factors

Alcohol Research Health the Journal of the National Institute on Alcohol Abuse and Alcoholism, Feb 1, 2006

tobacco; alcohol and other drug (AOD) use, abuse, and dependence; nicotine dependence; dual addic... more tobacco; alcohol and other drug (AOD) use, abuse, and dependence; nicotine dependence; dual addiction; brain; ventral tegmental area; mesolimbic dopamine system; animal models; genetic theory of alcohol and other drug use (AODU); cross-tolerance tine

Research paper thumbnail of Periadolescent and adult rats respond differently in tests measuring the rewarding and aversive effects of nicotine

Psychopharmacologia, Apr 4, 2006

Rationale: Initiation of tobacco use typically begins during adolescence, and the nature of these... more Rationale: Initiation of tobacco use typically begins during adolescence, and the nature of these first experiences with nicotine may affect the probability of continued use. In rodents, a number of studies suggest that periadolescents are more responsive to the rewarding effects of nicotine compared to adults. Objectives: This study was designed to determine if there are age differences in the rewarding and aversive effects of nicotine by using the conditioned place preference (CPP) and conditioned taste avoidance (CTA) paradigms, respectively. We also examined age differences in locomotor responses to nicotine. Methods: In the CPP paradigm, male periadolescent and adult Wistar rats received nicotine (0.2, 0.4, or 0.8 mg/kg, s.c.) or vehicle prior to place conditioning trials. In the CTA paradigm, in separate groups of rats, periadolescents and adults were exposed to a 0.1% saccharin solution, followed by the administration of nicotine (0.2, 0.4, or 0.8 mg/kg, s.c.) or vehicle. Four saccharinnicotine pairings were followed by a preference test and three extinction sessions. Results: In the CPP paradigm, nicotine produced a dose-dependent place preference in periadolescent, but not in adult, rats. In the CTA paradigm, adult rats expressed a dose-dependent avoidance of saccharin after pairings with nicotine, whereas periadolescents were resistant to CTA formation. With regard to locomotor activity, adults and periadolescents showed comparable locomotor responses to nicotine.

Research paper thumbnail of Effect of prazosin and guanfacine on stress-induced reinstatement of food and alcohol seeking in rats

Appetite, 2011

Relapse to alcohol use during abstinence or maladaptive eating habits during dieting is often pro... more Relapse to alcohol use during abstinence or maladaptive eating habits during dieting is often provoked by stress. The anxiogenic drug yohimbine, a prototypical ␣-2 adrenoceptor antagonist, which causes stress-like responses in humans and non-humans, reliably reinstates alcohol and food seeking in a rat relapse model. Here, we studied the effect of the ␣-1 adrenoceptor antagonist prazosin and the ␣-2 adrenoceptor agonist guanfacine on yohimbine-induced reinstatement. In Exp. 1, we trained rats to self-administer alcohol, and after extinction of alcohol-reinforced lever pressing, we tested prazosin's or guanfacine's effect on yohimbine-induced reinstatement; we also examined prazosin's effect on footshockstress-induced reinstatement. In Exp. 2, we trained food-restricted rats to self-administer food pellets and first examined prazosin's or guanfacine's effects on food-reinforced responding, and then, after extinction of lever presses, on yohimbine-induced reinstatement. Prazosin blocked yohimbine-induced reinstatement of food and alcohol seeking, as well as footshock-induced reinstatement of alcohol seeking. Guanfacine attenuated yohimbine-induced reinstatement of alcohol seeking at the highest dose, but its effect on yohimbine-induced reinstatement of food seeking was not significant. Neither prazosin nor guanfacine affected high-rate food-reinforced responding. Results demonstrate an important role of postsynaptic ␣-1 adrenoceptors in stress-induced reinstatement of alcohol and food seeking.

Research paper thumbnail of Stress-Induced Reinstatement of Drug Seeking: 20 Years of Progress

Neuropsychopharmacology, 2015

In human addicts, drug relapse and craving are often provoked by stress. Since 1995, this clinica... more In human addicts, drug relapse and craving are often provoked by stress. Since 1995, this clinical scenario has been studied using a rat model of stress-induced reinstatement of drug seeking. Here, we first discuss the generality of stress-induced reinstatement to different drugs of abuse, different stressors, and different behavioral procedures. We also discuss neuropharmacological mechanisms, and brain areas and circuits controlling stress-induced reinstatement of drug seeking. We conclude by discussing results from translational human laboratory studies and clinical trials that were inspired by results from rat studies on stress-induced reinstatement. Our main conclusions are: (1) The phenomenon of stress-induced reinstatement, first shown with an intermittent footshock stressor in rats trained to self-administer heroin, generalizes to other abused drugs, including cocaine, methamphetamine, nicotine, and alcohol, and is also observed in the conditioned place preference model in rats and mice. This phenomenon, however, is stressor-specific and not all stressors induce reinstatement of drug seeking. (2) Neuropharmacological studies indicate the involvement of corticotropin-releasing factor (CRF), noradrenaline, dopamine, glutamate, kappa/dynorphin, and several other peptide and neurotransmitter systems in stress-induced reinstatement. Neuropharmacology and circuitry studies indicate the involvement of CRF and noradrenaline transmission in bed nucleus of stria terminalis and central amygdala, and dopamine, CRF, kappa/dynorphin, and glutamate transmission in other components of the mesocorticolimbic dopamine system (ventral tegmental area, medial prefrontal cortex, orbitofrontal cortex, and nucleus accumbens). (3) Translational human laboratory studies and a recent clinical trial study show the efficacy of alpha-2 adrenoceptor agonists in decreasing stress-induced drug craving and stress-induced initial heroin lapse.Neuropsychopharmacology accepted article preview online, 15 May 2015. doi:10.1038/npp.2015.142.

Research paper thumbnail of Effects of pharmacological stressors on c-fos and CRF mRNA in mouse brain: Relationship to alcohol seeking

Neuroscience Letters, Sep 1, 2008

A marked heterogeneity exists among stressors in their ability to reinstate alcohol seeking in ra... more A marked heterogeneity exists among stressors in their ability to reinstate alcohol seeking in rats. We have reported that the pharmacological stressor yohimbine, an alpha-2 adrenoceptor antagonist, potently reinstated alcohol seeking, but FG-7142, a benzodiazepine inverse agonist was ineffective. In rats, we determined that yohimbine elicits patterns of brain expression of the mRNAs for c-fos, a marker of neuronal activation, and corticotropin-releasing factor (CRF) a stress-related peptide, distinct from that produced by FG-7142. The purpose of the present experiment is to determine if these differential effects of yohimbine and FG-7142 on regional c-fos and CRF mRNA expression generalize to another animal commonly used in alcohol research, the C57 BL/6J mouse. In comparing the results of the present study to those of our previous one, we found a number of commonalities in the patterns of activation elicited by yohimbine and FG-7142 between the two species, and some notable differences. As we found in the rat, yohimbine selectively increased c-fos mRNA in the mouse NACs, BLA and CeA. Yohimbine increased CRF mRNA only in the mouse PVN, but was without effect on CRF mRNA in extrahypothalamic sites, the BNST and CeA. This differs from what we saw in the rat, where yohimbine increased CRF mRNA in these extrahypothalamic regions, but not the PVN. The selective induction of c-fos in the NACs, BLA and CeA of mice and rats by yohimbine offers further support for the idea that activation of these structures participates in reinstatement induced by such stressors.

Research paper thumbnail of The CRF 1 receptor antagonist antalarmin attenuates yohimbine-induced increases in operant alcohol self-administration and reinstatement of alcohol seeking in rats

Psychopharmacology, 2007

Yohimbine is an alpha-2 adrenoreceptor antagonist that provokes stress- and anxiety-like response... more Yohimbine is an alpha-2 adrenoreceptor antagonist that provokes stress- and anxiety-like responses in both humans and laboratory animals. In rats, yohimbine increases operant alcohol self-administration and reinstates alcohol seeking. In this study, we assess whether these effects of yohimbine are attenuated by systemic injections of the corticotrotropin-releasing factor 1 (CRF1) receptor antagonist antalarmin. In Exp. 1, we trained rats to lever press for alcohol solutions (12% w/v, 1 h/day) over several weeks; during training, the response requirement was increased from a fixed-ratio-1 (FR-1) to a fixed-ratio-3 (FR-3) reinforcement schedule. We then tested the effect of antalarmin (10 or 20 mg/kg) on yohimbine (1.25 mg/kg)-induced increases in operant alcohol self-administration (FR-3 reinforcement schedule). Subsequently, we assessed the effect of antalarmin on yohimbine-induced increases in plasma corticosterone levels in the previously self-administering rats. In Exp. 2, we trained the rats to self-administer alcohol as in Exp. 1, and after extinction of the alcohol-reinforced lever responding over 13 days, we tested antalarmin's effect on yohimbine-induced reinstatement of alcohol seeking. Yohimbine increased operant alcohol self-administration and reinstated alcohol seeking after extinction. These effects of yohimbine were attenuated by antalarmin. Antalarmin injections in the absence of yohimbine had no effect on either operant alcohol self-administration or extinction responding. Antalarmin had no effect on yohimbine-induced corticosterone release in alcohol-experienced rats. These results suggest that extrahypothalamic CRF1 receptors are involved in the effect of yohimbine on operant alcohol self-administration and on relapse to alcohol seeking and support the notion that CRF1 receptor antagonists should be considered in alcohol addiction treatment.

Research paper thumbnail of IncreasedVulnerabilitytoNicotineSelf-Administrationand RelapseinAlcohol-NaiveOffspringofRatsSelectivelyBred forHighAlcoholIntake

The prevalence of smoking in human alcoholics is substantially higher than in the general populat... more The prevalence of smoking in human alcoholics is substantially higher than in the general population, and results from twin studies suggest that a shared genetic vulnerability underlies alcohol and nicotine addiction. Here, we directly tested this hypothesis by examining nicotine-taking behavior in alcohol-naive offspring of alcohol-preferring (P) rats and alcohol-nonpreferring (NP) rats that had been selectively bred for high and low alcohol intake. The self-administration of intravenous nicotine (0.015-0.060 mg/kg per infusion) in P rats was more than twice than that of NP rats. Nicotine seeking induced by reexposure to nicotine cues in extinction tests was also substantially greater in P rats than in NP rats. In a subsequent relapse test, priming nicotine injections reinstated drug seeking in P rats but not NP rats. P rats also self-administered higher amounts of oral sucrose (1-20%) than NP rats, a finding consistent with previous reports. In contrast, self-administration of intravenous cocaine (0.1875-1.125 mg/kg per infusion) was remarkably similar in the P and NP rats; however, P-NP differences in cocaine seeking emerged in subsequent extinction and cocaine priming-induced reinstatement tests. In both cases, lever responding was higher in P rats than in NP rats. Thus, alcohol-naive offspring of rats genetically selected for high alcohol intake are highly susceptible to nicotine self-administration and relapse, and this susceptibility is not likely caused by general reward deficits in NP rats. The present findings provide experimental evidence for the hypothesis that a shared genetic determinant accounts for the co-abuse of nicotine and alcohol.

Research paper thumbnail of Shaham Y, Funk D, Erb S, Brown TJ, Walker CD, Stewart J. Corticotropin-releasing factor, but not corticosterone, is involved in stress-induced relapse to heroin-seeking in rats. J Neurosci 17: 2605-2614

The Journal of Neuroscience : The Official Journal of the Society for Neuroscience

We showed previously that brief footshock stress and priming injections of heroin reinstate heroi... more We showed previously that brief footshock stress and priming injections of heroin reinstate heroin-seeking after prolonged drug-free periods. Here, we examined whether the adrenal hormone, corticosterone, and brain corticotropin-releasing factor (CRF) were involved in such reinstatement. We tested the effects of adrenalectomy, chronic exposure to the corticosterone synthesis inhibitor metyrapone (100 mg/kg, s.c., twice daily), acute exposure to metyrapone, acute intracerebroventricular injections of CRF (0.3 and 1.0 g), and intracerebroventricular injections of the CRF antagonist ␣-helical CRF (3 and 10 g). Rats were trained to self-administer heroin (100 g/kg/ infusion, i.v.) for 12-14 d. Extinction sessions were given for 4 -8 d (saline substituted for heroin). Tests for reinstatement were given after priming injections of saline and of heroin (0.25 mg/kg, s.c.), and after intermittent footshock (15 or 30 min, 0.5 mA). Adrenalectomy (performed after training) did not affect reinstatement by heroin but appeared to potentiate the reinstatement by footshock. Chronic exposure to metyrapone (from the beginning of extinction) or an acute injection of metyrapone (3 hr before testing) did not alter the reinstatement of heroinseeking induced by footshock or heroin. Acute exposure to metyrapone alone potently reinstated heroin-seeking. In addition, acute exposure to CRF reinstated heroin-seeking, and the CRF antagonist ␣-helical CRF attenuated stress-induced relapse. The effect of the CRF antagonist on reinstatement by heroin was less consistent. These results suggest that CRF, a major brain peptide involved in stress, contributes to relapse to heroin-seeking induced by stressors.

Research paper thumbnail of Stress- and pellet-priming-induced reinstatement of food seeking and neuronal activation in c-fos-GFP transgenic female rats. Role of ovarian hormones

Appetite, 2011

Relapse to alcohol use during abstinence or maladaptive eating habits during dieting is often pro... more Relapse to alcohol use during abstinence or maladaptive eating habits during dieting is often provoked by stress. The anxiogenic drug yohimbine, a prototypical ␣-2 adrenoceptor antagonist, which causes stress-like responses in humans and non-humans, reliably reinstates alcohol and food seeking in a rat relapse model. Here, we studied the effect of the ␣-1 adrenoceptor antagonist prazosin and the ␣-2 adrenoceptor agonist guanfacine on yohimbine-induced reinstatement. In Exp. 1, we trained rats to self-administer alcohol, and after extinction of alcohol-reinforced lever pressing, we tested prazosin's or guanfacine's effect on yohimbine-induced reinstatement; we also examined prazosin's effect on footshockstress-induced reinstatement. In Exp. 2, we trained food-restricted rats to self-administer food pellets and first examined prazosin's or guanfacine's effects on food-reinforced responding, and then, after extinction of lever presses, on yohimbine-induced reinstatement. Prazosin blocked yohimbine-induced reinstatement of food and alcohol seeking, as well as footshock-induced reinstatement of alcohol seeking. Guanfacine attenuated yohimbine-induced reinstatement of alcohol seeking at the highest dose, but its effect on yohimbine-induced reinstatement of food seeking was not significant. Neither prazosin nor guanfacine affected high-rate food-reinforced responding. Results demonstrate an important role of postsynaptic ␣-1 adrenoceptors in stress-induced reinstatement of alcohol and food seeking.

Research paper thumbnail of Effect of prazosin and guanfacine on stress-induced reinstatement of alcohol and food seeking in rats

Psychopharmacology, 2011

Rationale and Objectives-Relapse to alcohol use during abstinence or maladaptive eating habits du... more Rationale and Objectives-Relapse to alcohol use during abstinence or maladaptive eating habits during dieting is often provoked by stress. The anxiogenic drug yohimbine, which causes stress-like responses in humans and nonhumans, reliably reinstates alcohol and food seeking in a rat relapse model. Yohimibine is a prototypical alpha-2 adrenoceptor antagonist but results from studies on noradrenaline's role in yohimbine-induced reinstatement of drug and food seeking are inconclusive. Here we further addressed this issue by studying the effect of the alpha-1 adrenoceptor antagonist prazosin and the alpha-2 adrenoceptor agonist guanfacine on yohimbineinduced reinstatement.

Research paper thumbnail of Stress-Induced Reinstatement of Drug Seeking: 20 Years of Progress

Neuropsychopharmacology : official publication of the American College of Neuropsychopharmacology, Jan 15, 2015

In human addicts, drug relapse and craving are often provoked by stress. Since 1995, this clinica... more In human addicts, drug relapse and craving are often provoked by stress. Since 1995, this clinical scenario has been studied using a rat model of stress-induced reinstatement of drug seeking. Here, we first discuss the generality of stress-induced reinstatement to different drugs of abuse, different stressors, and different behavioral procedures. We also discuss neuropharmacological mechanisms, and brain areas and circuits controlling stress-induced reinstatement of drug seeking. We conclude by discussing results from translational human laboratory studies and clinical trials that were inspired by results from rat studies on stress-induced reinstatement. Our main conclusions are: (1) The phenomenon of stress-induced reinstatement, first shown with an intermittent footshock stressor in rats trained to self-administer heroin, generalizes to other abused drugs, including cocaine, methamphetamine, nicotine, and alcohol, and is also observed in the conditioned place preference model in r...

Research paper thumbnail of Corticotropin-releasing factor, but not corticosterone, is involved in stress-induced relapse to heroin-seeking in rats

The Journal of neuroscience : the official journal of the Society for Neuroscience, 1997

We showed previously that brief footshock stress and priming injections of heroin reinstate heroi... more We showed previously that brief footshock stress and priming injections of heroin reinstate heroin-seeking after prolonged drug-free periods. Here, we examined whether the adrenal hormone, corticosterone, and brain corticotropin-releasing factor (CRF) were involved in such reinstatement. We tested the effects of adrenalectomy, chronic exposure to the corticosterone synthesis inhibitor metyrapone (100 mg/kg, s.c., twice daily), acute exposure to metyrapone, acute intracerebroventricular injections of CRF (0.3 and 1.0 microgram), and intracerebroventricular injections of the CRF antagonist alpha-helical CRF (3 and 10 micrograms). Rats were trained to self-administer heroin (100 micrograms/kg/infusion, i.v.) for 12-14 d. Extinction sessions were given for 4-8 d (saline substituted for heroin). Tests for reinstatement were given after priming injections of saline and of heroin (0.25 mg/kg, s.c.), and after intermittent footshock (15 or 30 min, 0.5 mA). Adrenalectomy (performed after tra...

Research paper thumbnail of Effects of injections of 8-hydroxy-2-(di-n-propylamino)tetralin or muscimol in the median raphe nucleus on c-fos mRNA in the rat brain

Neuroscience, 2005

Inhibition of the median raphe nucleus (MRN) by the local injection of 5-HT(1A) or GABA(A) recept... more Inhibition of the median raphe nucleus (MRN) by the local injection of 5-HT(1A) or GABA(A) receptor agonists produces strong activational effects on feeding, drinking and locomotor activity. Using an animal model of relapse, we have shown that intra-MRN injection of the 5-HT(1A) autoreceptor agonist 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT) reinstates alcohol seeking in rats. The circuitry underlying the behavioral effects of intra-MRN injection of these drugs is not known. In order to identify the brain areas that may be involved, we measured levels of mRNA of the immediate early gene c-fos in discrete nuclei of the rat brain following intra-MRN infusions of these drugs. Male Wistar rats received intra-MRN infusions of 8-OH-DPAT (1 mug), muscimol (25 ng) or saline vehicle immediately prior to placement in locomotor activity chambers. Thirty minutes later, they were decapitated, and their brains processed for in situ hybridization of c-fos mRNA. In agreement with previous r...

Research paper thumbnail of Effect of blockade of corticotropin-releasing factor receptors in the median raphe nucleus on stress-induced c-fos mRNA in the rat brain

Neuroscience, 2003

Using a rat relapse model, we have shown that infusion of a corticotropin-releasing factor (CRF) ... more Using a rat relapse model, we have shown that infusion of a corticotropin-releasing factor (CRF) receptor antagonist into the median raphe nucleus (MRN) blocks footshock stress-induced reinstatement of alcohol seeking in rats. The goal of the present study was to begin identifying brain sites potentially involved in this effect. For this purpose, we measured levels of c-fos mRNA in discrete nuclei of the rat brain following exposure to intermittent footshock, which was preceded by intra-MRN infusions of a CRF receptor antagonist, d-Phe CRF (0 or 50 ng). Exposure to intermittent footshock increased the expression of c-fos mRNA in a number of brain regions previously shown to be responsive to stressful stimuli. Pretreatment with d-Phe CRF in the MRN selectively attenuated the increases in c-fos mRNA induced by footshock in the central nucleus of the amygdala (CeA). These findings are consistent with previous data on the important role for the CeA in stress-induced reinstatement of dru...

Research paper thumbnail of The role of kappa opioid receptors in stress-induced reinstatement of alcohol seeking in rats

Brain and Behavior, 2014

Introduction: Stress is related to heavy alcohol use and relapse in alcoholics. Using the reinsta... more Introduction: Stress is related to heavy alcohol use and relapse in alcoholics. Using the reinstatement model, we have shown that corticotropin-releasing factor (CRF) underlies stress-induced relapse to alcohol seeking in laboratory rodents. Little is known about how other neurotransmitters interact with CRF in these effects. Dynorphin and its receptor (kappa opioid receptor, KOR) are involved in stress responses and in alcohol seeking. KOR and CRF receptors (CRF R) may interact in the production of stress-related behaviors but it is not known whether this interaction is involved in reinstatement of alcohol seeking. Methods: Male Long Evans rats were trained to self-administer alcohol (12% w/v). After extinction of responding, we determined the effects of the KOR agonist, U50,488 (2.5, 5 mg/kg) on reinstatement of alcohol seeking, and their sensitivity to the selective KOR antagonist nor-binaltorphimine dihydrochloride (nor-BNI) (10 mg/kg) administered at different times before U50,488. We then examined the effects of nor-BNI on reinstatement induced by the stressor yohimbine (1.25 mg/kg) and on reinstatement induced by exposure to alcoholassociated cues . Finally, we determined whether CRF R1 blockade with antalarmin (10, 20 mg/kg) attenuates alcohol seeking induced by U50,488. Results: U50,488 reinstated alcohol seeking. Prior treatment with nor-BNI 2, but not 24 h before administration of U50,488 or yohimbine blocked reinstatement induced by these drugs. Cue-induced reinstatement was blocked by nor-BNI administered 2 h prior to testing. Finally, U50,488-induced reinstatement was blocked by antalarmin. Conclusions: These data further support a role for KOR in reinstatement of alcohol seeking under nonstress and stressful conditions and that KOR and CRF R interact in these effects.

Research paper thumbnail of The CRF1 receptor antagonist antalarmin attenuates yohimbine-induced increases in operant alcohol self-administration and reinstatement of alcohol seeking in rats

Psychopharmacology, 2007

Yohimbine is an alpha-2 adrenoreceptor antagonist that provokes stress- and anxiety-like response... more Yohimbine is an alpha-2 adrenoreceptor antagonist that provokes stress- and anxiety-like responses in both humans and laboratory animals. In rats, yohimbine increases operant alcohol self-administration and reinstates alcohol seeking. In this study, we assess whether these effects of yohimbine are attenuated by systemic injections of the corticotrotropin-releasing factor 1 (CRF1) receptor antagonist antalarmin. In Exp. 1, we trained rats to lever press for alcohol solutions (12% w/v, 1 h/day) over several weeks; during training, the response requirement was increased from a fixed-ratio-1 (FR-1) to a fixed-ratio-3 (FR-3) reinforcement schedule. We then tested the effect of antalarmin (10 or 20 mg/kg) on yohimbine (1.25 mg/kg)-induced increases in operant alcohol self-administration (FR-3 reinforcement schedule). Subsequently, we assessed the effect of antalarmin on yohimbine-induced increases in plasma corticosterone levels in the previously self-administering rats. In Exp. 2, we trained the rats to self-administer alcohol as in Exp. 1, and after extinction of the alcohol-reinforced lever responding over 13 days, we tested antalarmin's effect on yohimbine-induced reinstatement of alcohol seeking. Yohimbine increased operant alcohol self-administration and reinstated alcohol seeking after extinction. These effects of yohimbine were attenuated by antalarmin. Antalarmin injections in the absence of yohimbine had no effect on either operant alcohol self-administration or extinction responding. Antalarmin had no effect on yohimbine-induced corticosterone release in alcohol-experienced rats. These results suggest that extrahypothalamic CRF1 receptors are involved in the effect of yohimbine on operant alcohol self-administration and on relapse to alcohol seeking and support the notion that CRF1 receptor antagonists should be considered in alcohol addiction treatment.

Research paper thumbnail of Blunted cortisol rhythm is associated with learning impairment in aged hamsters

Physiology & behavior, Jan 15, 2004

In mammals, the cognitive decline that accompanies unsuccessful aging is associated with circadia... more In mammals, the cognitive decline that accompanies unsuccessful aging is associated with circadian rhythm dysfunction and increased levels of circulating glucocorticoids. The possible causal relations among these factors are not known. To test for primary effects of circadian clock dysfunction versus increased glucocorticoid levels as contributors to age-related learning impairment, we measured cortisol and wheel-running rhythms along with context learning in aged hamsters (15-18 months). At this age, locomotor rhythms of learners and nonlearners were found to be indistinguishable. However, plasma cortisol levels were lower, and the amplitude of the cortisol rhythm was reduced in the impaired animals. These data suggest that age-related cognitive decline may be related more to a loss of hormone rhythmicity than to a loss of behavioral rhythmicity or an increase in hormone level.

Research paper thumbnail of Biological processes underlying co-use of alcohol and nicotine: neuronal mechanisms, cross-tolerance, and genetic factors

Alcohol research & health : the journal of the National Institute on Alcohol Abuse and Alcoholism, 2006

Alcohol and nicotine are two of the oldest and most commonly used recreational drugs, and many pe... more Alcohol and nicotine are two of the oldest and most commonly used recreational drugs, and many people use both of them together. Although their ready availability likely contributes to the strong correlation between alcohol and nicotine use, several lines of evidence suggest that biological factors play a role as well. For example, both alcohol and nicotine act on a brain system called the mesolimbic dopamine system, which mediates the rewarding and reinforcing properties of both drugs. Modification of the activities of the mesolimbic dopamine system can interfere with the effects of both alcohol and nicotine. Another mechanism that may contribute to alcohol-nicotine interactions is cross-tolerance to the effects of both drugs. Finally, genetic studies in humans and of selectively bred mouse and rat strains suggest that shared genetic factors help determine a person's liability to use or abuse both alcohol and nicotine.

Research paper thumbnail of Intra-median raphe nucleus (MRN) infusions of muscimol, a GABA-A receptor agonist, reinstate alcohol seeking in rats: role of impulsivity and reward

Psychopharmacology, 2008

We previously found that the inhibition of median raphe nucleus (MRN) 5-HT transmission by local ... more We previously found that the inhibition of median raphe nucleus (MRN) 5-HT transmission by local injections of a 5-HT1A agonist 8-OH-DPAT or corticotrophin-releasing factor (CRF) mimic the effect of foot shock stress to reinstate alcohol seeking. In this study, we further explored the role of the MRN by examining the effect of inhibition of MRN neurons, by injecting the GABA-A receptor agonist muscimol, on the reinstatement of alcohol seeking. Male rats were trained to lever press for 12% alcohol. Cannulae were implanted aimed at the MRN; some rats were also given intra-MRN injections of 5,7-DHT to destroy ascending 5-HT neurons. After retraining, alcohol responding was extinguished for 14 days. Subsequently, we tested the effect of muscimol injections into the MRN (0, 12.5, 25, 50 ng) on reinstatement. We also tested the effect of MRN muscimol injections on a measure of reward, conditioned place preference (CPP) and performance in the five-choice serial reaction time task (5-CSRTT)...