Excessive cocaine use results from decreased phasic dopamine signaling in the striatum (original) (raw)
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Proceedings of the National Academy of Sciences of the United States of America, 2012
Drug addiction is a neuropsychiatric disorder that marks the end stage of a progression beginning with recreational drug taking but culminating in habitual and compulsive drug use. This progression is considered to reflect transitions among multiple neural loci. Dopamine neurotransmission in the ventromedial striatum (VMS) is pivotal in the control of initial drug use, but emerging evidence indicates that once drug use is well established, its control is dominated by the dorsolateral striatum (DLS). In the current work, we conducted longitudinal neurochemical recordings to ascertain the spatiotemporal profile of striatal dopamine release and to investigate how it changes during the period from initial to established drug use. Dopamine release was detected using fast-scan cyclic voltammetry simultaneously in the VMS and DLS of rats bearing indwelling i.v. catheters over the course of 3 wk of cocaine self-administration. We found that phasic dopamine release in DLS emerged progressively during drug taking over the course of weeks, a period during which VMS dopamine signaling declined. This emergent dopamine signaling in the DLS mediated discriminated behavior to obtain drug but did not promote escalated or compulsive drug use. We also demonstrate that this recruitment of dopamine signaling in the DLS is dependent on antecedent activity in VMS circuitry. Thus, the current findings identify a striatal hierarchy that is instantiated during the expression of established responses to obtain cocaine. D rug use often begins as a recreational behavior driven by the rewarding properties of the abused drug. However, addiction is characterized by habitual and compulsive drug use in which other factors, such as withdrawal symptoms, stress, and drug-associated conditioned stimuli (CS), also contribute to the motivation to consume drugs, and drug taking becomes increasingly prioritized over other behaviors (1). A wealth of evidence shows that the mesolimbic dopamine projection from the ventral tegmental area to the ventromedial striatum (VMS) is central to drug reinforcement (2). The ambient concentration of dopamine in the VMS is increased when animals self-administer drugs of abuse, including cocaine (3), and animals maintain this elevated dopamine level by regulating their rate of responding for drug (4). In addition, with repeated pairing of environmental stimuli with the drug, these CS also gain the propensity to elicit changes in dopamine concentration in the VMS (5-8); and even though these phasic neurochemical responses last only a few seconds, they are capable of controlling drug-seeking and -taking behavior (5). Together, these results implicate dopamine release in the VMS as a critical substrate in the control of drug use .
Increased Occupancy of Dopamine Receptors in Human Striatum during Cue-Elicited Cocaine Craving
Neuropsychopharmacology, 2007
In all, 19 research subjects, with current histories of frequent cocaine use, were exposed to cocaine-related cues to elicit drug craving. We measured the change of occupancy of dopamine at D2-like receptors with positron emission tomography (PET) and inferred a change of intrasynaptic dopamine (endogenous dopamine release), based on the displacement of radiotracer [ 11 C]raclopride. Receptor occupancy by dopamine increased significantly in putamen of participants who reported cue-elicited craving compared to those who did not. Further, the intensity of craving was positively correlated with the increase in dopamine receptor occupancy in the putamen. These results provide direct evidence that occupancy of dopamine receptors in human dorsal striatum increased in proportion to subjective craving, presumably because of increased release of intrasynaptic dopamine.
The Journal of neuroscience : the official journal of the Society for Neuroscience, 2011
Chronic exposure to drugs of abuse alters brain reward circuits and produces functional changes in the dopamine (DA) system. However, it is not known whether these changes are directly related to drug-driven behaviors or whether they simply are adaptive responses to long-term drug exposure. Here, we combined the rat model of cocaine self-administration with brain slice electrophysiology to identify drug-use related alterations in the neuromodulatory effects of DA in the oval bed nucleus of the stria terminalis (ovBST), a robust DA terminal field. Long-Evans rats self-administered cocaine intravenously (0.75 mg/kg/injection) for an average of 15 d, on reward-lean or -rich schedules of reinforcement. Brain slice recordings conducted 20 h after the last self-administration session revealed a reversal of the neuromodulatory effect of DA on GABA(A)-IPSCs. Specifically, the effect of DA switched from a D2-mediated decrease in drug-naive rats to a D1-receptor-mediated increase in GABA(A)-I...
Cocaine Seeking And Taking Are Oppositely Regulated By Dopamine
In some individuals, drug-associated cues subsume potent control of behavior, such as the elicitation of drug craving1–3and automatized drug use4. The intensity of this cue reactivity is highly predictive of relapse and other clinical outcomes in substance use disorders5, 6. It has been postulated that this cue reactivity is driven by augmentation of dopamine release over the course of chronic drug use7. Here we carried out longitudinal recording and manipulation of cue-evoked dopamine signaling across phases of substance-use related behavior in rats. We observed a subset of individuals that exhibited increased cue reactivity and escalated drug consumption, two cardinal features of substance use disorders. In these individuals, cue-evoked phasic dopamine release underwent diametrically opposed changes in amplitude, determined by the context in which the cue is presented. Dopamine evoked by non-contingent cue presentation increased over drug use, producing greater cue reactivity; whe...
American Journal of Psychiatry, 2014
Previous research has shown that dopamine signaling in the limbic striatum is crucial for selecting adaptive, motivated behavior, and that disrupted dopamine transmission is associated with impulsive and maladaptive behavior. In humans, Positron Emission Tomography (PET) imaging studies have shown that cocaine dependence is associated with the dysregulation of striatal dopamine signaling, which is associated with cocaine seeking behavior. The goal of the present study was to investigate whether this association applies to the treatment setting. Our hypothesis was that dopamine signaling in the limbic striatum would be associated with response to a behavioral treatment that uses positive reinforcement to replace impulsive cocaine use with constructive personal goals. Prior to treatment, cocaine dependent subjects underwent two PET scans using [ 11 C]raclopride, before and after the administration of a stimulant (methylphenidate), to measure striatal D 2/3 receptor binding and pre-synaptic dopamine release. The results showed that both of these outcome measures were reduced in the volunteers who failed to respond to treatment compared to those who experienced a positive treatment response. These findings provide insight into the neurochemistry of treatment response and show that low dopamine transmission is associated with treatment failure. In addition, these data suggest that the combination of behavioral treatment with methods that increase striatal dopamine signaling might serve as a therapeutic strategy for cocaine dependence.
American Journal of Psychiatry, 2011
Previous research has shown that dopamine signaling in the limbic striatum is crucial for selecting adaptive, motivated behavior, and that disrupted dopamine transmission is associated with impulsive and maladaptive behavior. In humans, Positron Emission Tomography (PET) imaging studies have shown that cocaine dependence is associated with the dysregulation of striatal dopamine signaling, which is associated with cocaine seeking behavior. The goal of the present study was to investigate whether this association applies to the treatment setting. Our hypothesis was that dopamine signaling in the limbic striatum would be associated with response to a behavioral treatment that uses positive reinforcement to replace impulsive cocaine use with constructive personal goals. Prior to treatment, cocaine dependent subjects underwent two PET scans using [ 11 C]raclopride, before and after the administration of a stimulant (methylphenidate), to measure striatal D 2/3 receptor binding and pre-synaptic dopamine release. The results showed that both of these outcome measures were reduced in the volunteers who failed to respond to treatment compared to those who experienced a positive treatment response. These findings provide insight into the neurochemistry of treatment response and show that low dopamine transmission is associated with treatment failure. In addition, these data suggest that the combination of behavioral treatment with methods that increase striatal dopamine signaling might serve as a therapeutic strategy for cocaine dependence.
Journal of Neuroscience, 2013
Two of the most commonly used procedures to study the abuse-related effects of drugs in laboratory animals are intravenous drug self-administration and reinstatement of extinguished behavior previously maintained by drug delivery. Intravenous selfadministration is widely accepted to model ongoing drug-taking behavior, whereas reinstatement procedures are accepted to model relapse to drug taking following abstinence. Previous studies indicate that 5-HT 2A receptor antagonists attenuate the reinstatement of cocaine-maintained behavior but not cocaine self-administration in rodents. Although the abuse-related effects of cocaine have been closely linked to brain dopamine systems, no previous study has determined whether this dissociation is related to differential regulation of dopamine neurotransmission. To elucidate the neuropharmacological and neuroanatomical mechanisms underlying this phenomenon, we evaluated the effects of the selective 5-HT 2A receptor antagonist M100907 on intravenous cocaine self-administration and drugand cue-primed reinstatement in rhesus macaques (Macaca mulatta). In separate subjects, we evaluated the role of 5-HT 2A receptors in cocaine-induced dopamine overflow in the nucleus accumbens (n ϭ 4) and the caudate nucleus (n ϭ 5) using in vivo microdialysis. Consistent with previous studies, M100907 (0.3 mg/kg, i.m.) significantly attenuated drug-and cue-induced reinstatement but had no significant effects on cocaine self-administration across a range of maintenance doses. Importantly, M100907 (0.3 mg/kg, i.m.) attenuated cocaine-induced (1.0 mg/kg, i.v.) dopamine overflow in the caudate nucleus but not in the nucleus accumbens. These data suggest that important abuse-related effects of cocaine are mediated by distinct striatal dopamine projection pathways.