Candice Contet - Academia.edu (original) (raw)

Papers by Candice Contet

Neurobiology of Stress, 2020

Childhood adversity increases vulnerability to alcohol use disorders and preclinical models are n... more Childhood adversity increases vulnerability to alcohol use disorders and preclinical models are needed to investigate the underlying neurobiological mechanisms. The present study modeled early-life adversity by rearing male and female C57BL/6J mouse pups in a limited bedding and nesting (LBN) environment, which induces erratic maternal care. As adults, mice were given limited access to two-bottle choice (2BC) alcohol drinking, combined or not with chronic intermittent ethanol (CIE) vapor inhalation to induce alcohol dependence. We tested the hypothesis that LBN rearing might exacerbate or facilitate the emergence of the motivational and affective effects of CIE. Consistent with our hypothesis, although LBN-reared males consumed the same baseline levels of alcohol as controls, they escalated their ethanol intake at an earlier stage of CIE exposure, i.e., after 4 rounds vs. 5 rounds for controls. In contrast, females were insensitive to both LBN rearing and CIE exposure. Males were further subjected to a behavioral test battery. Withdrawal from CIE-2BC increased digging activity and lowered mechanical nociceptive thresholds regardless of early-life conditions. On the other hand, LBN-reared CIE-2BC males showed reduced open arm exploration in the elevated plus maze and increased immobility in the tail suspension test compared to alcohol-naïve counterparts, while no group differences were detected among control-reared males. Finally, LBN rearing and alcohol exposure did not affect grooming in response to a sucrose spray (splash test), novel object recognition, or corticosterone levels. In summary, the LBN experience accelerates the transition from moderate to excessive alcohol drinking and produces additional indices of affective dysfunction during alcohol withdrawal in C57BL/6J male mice.

Neuropharmacology, 2021

Alterations in the function of prefrontal cortex (PFC) and hippocampus have been implicated in un... more Alterations in the function of prefrontal cortex (PFC) and hippocampus have been implicated in underlying the relapse to alcohol seeking behaviors in humans and animal models of moderate to severe alcohol use disorders (AUD). Here we used chronic intermittent ethanol vapor exposure (CIE), 21d protracted abstinence following CIE (21d AB), and re-exposure to one vapor session during protracted abstinence (re-exposure) to evaluate the effects of chronic ethanol exposure on basal synaptic function, neuronal excitability and expression of key synaptic proteins that play a role in neuronal excitability in the PFC and dentate gyrus (DG). CIE consistently enhanced excitability of layer 2/3 pyramidal neurons in the PFC and granule cell neurons in the DG. In the DG, this effect persisted during 21d AB. Re-exposure did not enhance excitability, suggesting resistance to vapor-induced effects. Analysis of action potential kinetics revealed that altered afterhyperpolarization, rise time and decay time constants are associated with the altered

Proceedings of the National Academy of Sciences, 2020

Significance Visualizing functional changes in brain networks that are produced by alcohol use an... more Significance Visualizing functional changes in brain networks that are produced by alcohol use and alcohol dependence is a critical step in our understanding of the consequences of drinking alcohol. Because of technical limitations, visualizing changes throughout the whole brain at single-cell resolution has not been possible. The present study used a single-cell whole-brain imaging approach in mice to assess whether alcohol abstinence alters functional architecture of the brain. Compared with nondrinkers and casual drinkers, alcohol-dependent mice exhibited widespread increases in coordinated brain activity during abstinence and a decrease in modularity. We also identified target brain regions for future research and provide a single-cell whole-brain atlas that may be used to better understand the consequences of alcohol use, dependence, and abstinence.

Neuropsychopharmacology : official publication of the American College of Neuropsychopharmacology, Jan 4, 2014

The hypocretin/orexin (HCRT) system has been associated with both positive and negative drug rein... more The hypocretin/orexin (HCRT) system has been associated with both positive and negative drug reinforcement, implicating HCRT receptor 1 (HCRT-R1) signaling in drug-related behaviors for all major drug classes, including opioids. However, to date there are limited studies investigating the role of HCRT receptor 2 (HCRT-R2) signaling in compulsive-like drug seeking. Escalation of drug intake with extended access has been suggested to model the transition from controlled drug use to compulsive-like drug seeking/taking. The current study examined the effects of a HCRT-R2 antagonist, NBI-80713, on heroin self-administration in rats allowed short- (1 h; ShA) or long- (12 h; LgA) access to intravenous heroin self-administration. Results indicate that systemically administered NBI-80713 dose-dependently decreased heroin self-administration in LgA, but not in ShA, animals. Quantitative PCR analyses showed an increase in Hcrtr2 mRNA levels in the central amygdala, a stress-related brain regio...

Psychopharmacology, 2010

Rationale Testing genetically engineered mice in a reliable nicotine self-administration procedur... more Rationale Testing genetically engineered mice in a reliable nicotine self-administration procedure could provide important insights into the molecular mechanisms underlying nicotine reinforcement. Objectives We assessed operant responding for intravenous nicotine infusions in C57BL/6J male mice under a fixedratio 3 schedule of reinforcement in which a visual cue was contingently associated with drug delivery. Methods/Results Acquisition, dose-response function, extinction, and cue-induced reinstatement of operant behavior were characterized. Low nicotine doses (0.001-0.06 mg/kg/ infusion) elicited response rates similar to those supported by saline, whereas a higher dose (0.1 mg/kg/infusion) decreased responding. Using an identical procedure to assess cocaine self-administration in an independent group of mice yielded an inverted U-shaped dose-response curve. Other mice trained to respond exclusively for the visual stimulus earned a similar number of reinforcers as mice self-administering saline or low nicotine doses, although with a lower selectivity for the active lever and their response rates were sensitive to the discontinuation and resumption of cue light presentation. Finally, patterns of responding for nicotine, cocaine, or the visual stimulus alone were analyzed using frequency distributions of interresponse intervals and extended return maps. These analyses revealed unique properties of nicotine, which dose-dependently delayed the first response post-timeout and increased the regularity of lever pressing activity. Conclusions Nicotine did not enhance the reinforcing properties of the visual cue paired with drug delivery. Interestingly, however, patterns of responding could differentiate nicotine self-administration from responding for a visual stimulus or saline and indicated that nicotine functioned as a salient stimulus driving highly regular operant behavior.

Neuropharmacology, 2008

Acute morphine administration produces analgesia and reward, but prolonged use may lead to analge... more Acute morphine administration produces analgesia and reward, but prolonged use may lead to analgesic tolerance in patients chronically treated for pain and to compulsive intake in opioid addicts. Moreover, long-term exposure may induce physical dependence, manifested as somatic withdrawal symptoms in the absence of the drug. We set up three behavioral paradigms to model these adaptations in mice, using distinct regimens of repeated morphine injections to induce either analgesic tolerance, locomotor sensitization or physical dependence. Interestingly, mice tolerant to analgesia were not sensitized to hyperlocomotion, whereas sensitized mice displayed some analgesic tolerance. We then examined candidate molecular modifications that could underlie the development of each behavioral adaptation. First, analgesic tolerance was not accompanied by mu opioid receptor desensitization in the periaqueductal gray. Second, cdk5 and p35 protein levels were unchanged in caudate-putamen, nucleus accumbens and prefrontal cortex of mice displaying locomotor sensitization. Finally, naloxone-precipitated morphine withdrawal did not enhance basal or forskolin-stimulated adenylate cyclase activity in nucleus accumbens, prefrontal cortex, amygdala, bed nucleus of stria terminalis or periaqueductal gray. Therefore, the expression of behavioral adaptations to chronic morphine treatment was not associated with the regulation of micro opioid receptor, cdk5 or adenylate cyclase activity in relevant brain areas. Although we cannot exclude that these modifications were not detected under our experimental conditions, another hypothesis is that alternative molecular mechanisms, yet to be discovered, underlie analgesic tolerance, locomotor sensitization and physical dependence induced by chronic morphine administration.

Molecular and Cellular Biology, 2005

RGS proteins are negative regulators of signaling through heterotrimeric G protein-coupled recept... more RGS proteins are negative regulators of signaling through heterotrimeric G protein-coupled receptors and, as such, are in a position to regulate a plethora of biological phenomena. However, those have just begun to be explored in vivo. Here, we describe a mouse line deficient for Rgs4 , a gene normally expressed early on in discrete populations of differentiating neurons and later on at multiple sites of the central nervous system, the cortex in particular, where it is one of the most highly transcribed Rgs genes. Rgs4 lacZ/lacZ mice had normal neural development and were viable and fertile. Behavioral testing on mutant adults revealed subtle sensorimotor deficits but, so far, supported neither the proposed status of Rgs4 as a schizophrenia susceptibility gene (by showing intact prepulse inhibition in the mutants) nor (unlike another member of the Rgs family, Rgs9 ) a role of Rgs4 in the acute or chronic response to opioids.

Cell, 2009

Delta and mu opioid receptors (DORs and MORs) are inhibitory G protein-coupled receptors that rep... more Delta and mu opioid receptors (DORs and MORs) are inhibitory G protein-coupled receptors that reportedly cooperatively regulate the transmission of pain messages by substance P and TRPV1-expressing pain fibers. Using a DOReGFP reporter mouse we now show that the DOR and MOR are, in fact, expressed by different subsets of primary afferents. The MOR is expressed in peptidergic pain fibers, the DOR in myelinated and nonpeptidergic afferents. Contrary to the prevailing view, we demonstrate that the DOR is trafficked to the cell surface under resting conditions, independently of substance P, and internalized following activation by DOR agonists. Finally, we show that the segregated DOR and MOR distribution is paralleled by a remarkably selective functional contribution of the two receptors to the control of mechanical and heat pain, respectively. These results demonstrate that behaviorally relevant pain modalities can be selectively regulated through the targeting of distinct subsets of primary afferent pain fibers.

Behavioural Brain Research, 2001

In recent years the use of genetic manipulations to investigate the molecular mechanisms underlyi... more In recent years the use of genetic manipulations to investigate the molecular mechanisms underlying learning and memory has become a common approach. In a great many cases, the spatial learning ability of mutant mice has been assessed using the Morris watermaze task. The performance of these mice may, however, be strongly influenced by their genetic background and, therefore, the interpretation of their phenotype requires a preliminary characterization of the parental strains. The present study compared 129S2/Sv and C57/BL/6J inbred mouse strains, which have been widely used in deriving lines of genetically modified mice, on the hidden platform version of the watermaze task. During acquisition, the C57 mice displayed shorter escape latencies to find the platform than the 129S2s. Further analysis revealed, however, that the C57 mice also swam faster than the 129S2s. The analysis of path lengths was thus a more reliable measure of spatial learning, and revealed an equal level of performance in the two strains. This conclusion was confirmed during the two probe trials with both strains showing a similar spatial preference for the training site. These results suggest that the 129S2 substrain is no less proficient than the C57 substrain in terms of spatial learning in the watermaze, and also demonstrates the importance of not relying solely on escape latency as a measure of watermaze performance.

Addiction Biology, 2013

Ethanol exposure and withdrawal alter the generation of new neurons in the adult hippocampus. The... more Ethanol exposure and withdrawal alter the generation of new neurons in the adult hippocampus. The endogenous opioid system, in particular the μ opioid receptor (MOR), can modulate neural progenitors and also plays a critical role in ethanol drinking and dependence. In the present study, we sought to determine whether MOR contributes to the effects of ethanol on the dentate gyrus (DG) neurogenic niche. MOR wild-type (WT), heterozygous (Het) and knockout (KO) littermates were subjected to voluntary ethanol drinking in repeated limited-access two-bottle choice (2BC) sessions. MOR deficiency did not alter progenitor proliferation, neuronal differentiation and maturation, apoptosis or microglia in ethanol-naïve mice. When exposed to five consecutive weeks of 2BC, MOR mutant mice exhibited a gene-dosage dependent reduction of ethanol consumption compared to WT mice. Introducing a week of ethanol deprivation between each week of 2BC increased ethanol consumption in all genotypes and produced equivalent intakes in WT, Het and KO mice. Under the latter paradigm, ethanol drinking decreased progenitor proliferation and neuronal differentiation in the DG of WT mice. Interestingly, WT mice exhibited a strong negative correlation between ethanol intake and proliferation, which was disrupted in Het and KO mice. Moreover, MOR deficiency blocked the effect of ethanol on neuronal differentiation. MOR deficiency also protected against the neuroimmune response to ethanol drinking. Finally, chronic binge drinking induced a paradoxical decrease in apoptosis, which was independent of MOR. Altogether our data suggest that MOR is implicated in some of the neuroplastic changes produced by chronic ethanol exposure in the DG.

Addiction Biology, 2011

Alcoholism is characterized by a progressive loss of control over ethanol intake. The purpose of ... more Alcoholism is characterized by a progressive loss of control over ethanol intake. The purpose of this study was to identify transcriptional changes selectively associated with excessive ethanol drinking in dependent mice, as opposed to non-dependent mice maintaining a stable voluntary consumption or mice solely undergoing forced intoxication. We measured expression levels of 106 candidate genes in the extended amygdala, a key brain structure for the development of drug addiction. Cluster analysis identified 17 and 15 genes selectively induced or repressed, respectively, under conditions of excessive drinking. These genes belong to signaling pathways involved in neurotransmission and transcriptional regulation. Keywords alcoholism; C57BL/6J; clustering; ethanol dependence; extended amygdala; qPCR Alcoholism is defined as a maladaptive pattern of alcohol consumption, characterized by compulsive alcohol intake, loss of control over drinking and a negative emotional state during withdrawal (Koob 2003). The endogenous opioid system is recruited by all drugs of abuse, including alcohol, and transcriptional changes occurring downstream of mu opioid receptor activation may therefore contribute to the development of addiction (Gerrits et al. 2003). Our laboratory has previously identified a collection of 83 genes, whose expression is regulated in the extended amygdala in response to prolonged stimulation of the mu opioid receptor (Befort et al. 2008b). The present study aims to assess whether these genes, as well as 23 additional genes previously implicated in addiction (Befort et al. 2008a; Gerrits et al. 2003; Mulligan et al. 2006), are differentially expressed in ethanol-dependent mice, which voluntarily drink excessive amounts of ethanol. Gene expression was measured in the

Molecular Psychiatry, 2022

Corticotropin-releasing factor (CRF) signaling in the central nucleus of the amygdala (CeA) plays... more Corticotropin-releasing factor (CRF) signaling in the central nucleus of the amygdala (CeA) plays a critical role in rodent models of excessive alcohol drinking. However, the source of CRF acting in the CeA during alcohol withdrawal remains to be identified. In the present study, we hypothesized that CeA CRF interneurons may represent a behaviorally relevant source of CRF to the CeA increasing motivation for alcohol via negative reinforcement. We first observed that Crh mRNA expression in the anterior part of the mouse CeA correlates positively with alcohol intake in C57BL/6J males with a history of chronic binge drinking followed by abstinence and increases upon exposure to chronic intermittent ethanol (CIE) vapor inhalation. We then found that chemogenetic activation of CeA CRF neurons in Crh-IRES-Cre mouse brain slices increases gamma-aminobutyric acid (GABA) release in the medial CeA, in part via CRF1 receptor activation. While chemogenetic stimulation exacerbated novelty-induced feeding suppression (NSF) in alcohol-naïve mice, thereby mimicking the effect of withdrawal from CIE, it had no effect on voluntary alcohol consumption, following either acute or chronic manipulation. Furthermore, chemogenetic inhibition of CeA CRF neurons did not affect alcohol consumption or NSF in chronic alcohol drinkers exposed to air or CIE. Altogether, these findings indicate that Users may view, print, copy, and download text and data-mine the content in such documents, for the purposes of academic research, subject always to the

Large conductance potassium (BK) channels are among the most sensitive molecular targets of ethan... more Large conductance potassium (BK) channels are among the most sensitive molecular targets of ethanol. Whether the action of ethanol at BK channels influences the motivation to drink alcohol remains to be determined. In the present study, we sought to investigate the behavioral relevance of this interaction by introducing in the mouse genome a point mutation (BK α K361N) known to render BK channels insensitive to ethanol while preserving their physiological function. We demonstrate that preventing ethanol’s interaction with BK channels at this site hinders the escalation of voluntary alcohol intake induced by repeated cycles of alcohol intoxication and withdrawal. In contrast, the mutation does not alter ethanol’s acute behavioral effects, nor the metabolic and activity changes induced by chronic exposure to alcohol. Our findings point at BK channel ethanol-sensing capacity as a vulnerability mechanism in the transition from moderate alcohol consumption to pathological patterns of alc...

eneuro

The lateral amygdala (LA) serves as the point of entry for sensory information within the amygdal... more The lateral amygdala (LA) serves as the point of entry for sensory information within the amygdala complex, a structure that plays a critical role in emotional processes and has been implicated in alcohol use disorders. Within the amygdala, the corticotropin-releasing factor (CRF) system has been shown to mediate some of the effects of both stress and ethanol, but the effects of ethanol on specific CRF1 receptor circuits in the amygdala have not been fully established. We used male CRF1:GFP reporter mice to characterize CRF1-expressing (CRF1 1) and nonexpressing (CRF1 À) LA neurons and investigate the effects of acute and chronic ethanol exposure on these populations. The CRF1 1 population was found to be composed predominantly of glutamatergic projection neurons with a minority subpopulation of interneurons. CRF1 1 neurons exhibited a tonic conductance that was insensitive to acute ethanol. CRF1 À neurons did not display a basal tonic conductance, but the application of acute ethanol induced a d GABA A receptor subunit-dependent tonic conductance and enhanced phasic GABA release onto these cells. Chronic ethanol increased CRF1 1 neuronal excitability but did not significantly alter phasic or tonic GABA signaling in either CRF1 1 or CRF1 À cells. Chronic ethanol and withdrawal also did not alter basal extracellular GABA or glutamate transmitter levels in the LA/BLA and did not alter the sensitivity of GABA or glutamate to acute ethanol-induced increases in transmitter release. Together, these results provide the first characterization of the CRF1 1 population of LA neurons and suggest mechanisms for differential acute ethanol sensitivity within this region.

BackgroundCorticotropin-releasing factor (CRF) signaling in the central nucleus of the amygdala (... more BackgroundCorticotropin-releasing factor (CRF) signaling in the central nucleus of the amygdala (CeA) plays a critical role in rodent models of excessive alcohol drinking. However, the source of CRF acting in the CeA during alcohol withdrawal remains to be identified. In the present study, we hypothesized that CeA CRF interneurons may represent a behaviorally relevant source of CRF to the CeA increasing motivation for alcohol via negative reinforcement.MethodsWe tested this hypothesis in male mice and used chemogenetics to stimulate CeA CRF neurons in vitro and in vivo.ResultsWe first observed that Crh mRNA expression in the anterior part of the mouse CeA, at the junction with the interstitial nucleus of the posterior limb of the anterior commissure, correlates positively with alcohol intake in C57BL/6J males with a history of chronic binge drinking. We then found that chemogenetic activation of CeA CRF neurons in Crh-IRES-Cre mouse brain slices increases gamma-aminobutyric acid (GA...

Alcoholism: Clinical and Experimental Research

Neuropsychopharmacology : official publication of the American College of Neuropsychopharmacology, 2018

The hypocretin/orexin (HCRT) neuropeptide system regulates feeding, arousal state, stress respons... more The hypocretin/orexin (HCRT) neuropeptide system regulates feeding, arousal state, stress responses, and reward, especially under conditions of enhanced motivational relevance. In particular, HCRT neurotransmission facilitates drug-seeking behavior in circumstances that demand increased effort and/or motivation to take the drug. The present study used a shRNA-encoding adeno-associated viral vector to knockdown Hcrt expression throughout the dorsal hypothalamus in adult rats and determine the role of HCRT in cocaine self-administration. Chronic Hcrt silencing did not impact cocaine self-administration under short-access conditions, but robustly attenuated cocaine intake under extended access conditions, a model that mimics key features of compulsive cocaine taking. In addition, Hcrt silencing decreased motivation for both cocaine and a highly palatable food reward (i.e., sweetened condensed milk; SCM) under a progressive ratio schedule of reinforcement, but did not alter responding f...