A role for sensitization in craving and relapse in cocaine addiction

Drug addiction involves compulsive drug-seeking and drug-taking despite known adverse consequences. The enduring nature of drug addiction suggests that repeated exposure to abused drugs leads to stable alterations that likely involve changes in gene expression in the brain. The dopamine D1 receptor has been shown to mediate the long-term behavioral effects of cocaine. To examine how the persistent behavioral effects of cocaine correlate with underlying changes in gene expression, we have used D1 receptor mutant and wild-type mice to identify chronic cocaine-induced gene expression changes mediated via the D1 receptors. We focused on the caudoputamen and nucleus accumbens, two key brain regions that mediate the long-term effects of cocaine. Our analyses demonstrate that repeated cocaine administration induces changes in the expression of 109 genes, including those encoding the stromal cell-derived factor 1, insulin-like growth factor binding protein 6, sigma 1 receptor, regulators of G-protein signaling protein 4, Wnt1 responsive Cdc42 homolog, Ca 2 þ /calmodulin-dependent protein kinase II a subunit, and cyclin D2, via the D1 receptors. Moreover, the seven genes contain AP-1 binding sites in their promoter regions. These results suggest that genes encoding certain extracellular factors, membrane receptors and modulators, and intracellular signaling molecules, among others, are regulated by cocaine via the D1 receptor, and these AP-1 transcription complex-regulated genes might contribute to persistent cocaine-induced behavioral changes.

Section: Resultsmentioning

confidence: 99%

Repeated Cocaine Administration Induces Gene Expression Changes through the Dopamine D1 Receptors

Zhang

Tang

et al. 2005

“…Second, a causal link between the long-term expression of behavioral sensitization and sensitization of the mesolimbic DA system has been suggested (Kalivas and Duffy, 1993a;Vanderschuren and Kalivas, 2000). The failure of repeated ETOH intoxication to induce sensitization of the accumbens DA response suggests that repeated exposure to different drugs of abuse does not necessarily result in a common final neuroadaptation that triggers compulsive drug use or, alternatively, and contrary to a widely held notion, this common final neuroadaptation does not involve sensitization of the mesolimbic DA system (Kalivas et al, 1998;Robinson and Berridge, 2001). Of course, the fact that we failed to see sensitization of the DA response does not prove that it would not occur under other experimental conditions.…”

Section: Discussionmentioning

confidence: 99%

“…This phenomenon, referred to as behavioral sensitization, is manifested in rodents as an increase in drug-evoked locomotor activity after repeated drug administration. Behavioral sensitization is proposed to result from some of the same neuroadaptations that are triggered by repeated drug exposure and that lead to the development of compulsive drug use (Kalivas et al, 1998). One neuroadaptation that has received considerable attention involves the effects of repeated drug experience on the mesoaccumbal dopaminergic system.…”

Section: Introductionmentioning

confidence: 99%

Repeated Ethanol Intoxication Induces Behavioral Sensitization in the Absence of a Sensitized Accumbens Dopamine Response in C57BL/6J and DBA/2J Mice

Zapata

Gonzales

Shippenberg

2005

Repeated exposure to drugs of abuse results in an increased sensitivity to their behavioral effects, a phenomena referred to as behavioral sensitization. It has been suggested that the same neuroadaptations underlying behavioral sensitization contribute to the maintenance and reinstatement of addiction. Dysregulation of dopamine (DA) neurotransmission in the mesoaccumbens system is one neuroadaptation that is thought to lead to the compulsive drug-seeking that characterizes addiction. Evidence that sensitization to psychostimulants and opiates is associated with an enhancement of drug-evoked DA levels in the nucleus accumbens has also been obtained. Like other drugs of abuse, the acute administration of ethanol (ETOH) stimulates DA release in this brain region. Moreover, repeated ETOH experience results in an enhanced behavioral response to a subsequent ethanol challenge. Data regarding the influence of repeated ethanol intoxication and withdrawal upon mesoaccumbal DA neurotransmission is limited. Studies examining ETOH-evoked alterations in mesoaccumbal DA neurotransmission as a function of withdrawal duration are lacking. The present experiments quantified basal and ethanol-evoked DA levels 14 days and 24 h following the cessation of a repeated ETOH intoxication protocol, which results in sensitization to the locomotor activating effects of ethanol. Locomotor activity was assessed in parallel groups of animals. Studies were conducted in two mouse strains, C57BL/6J and DBA/2J, which differ in their behavioral responses to ETOH. The results indicate the development of transient tolerance to both ETOH-induced behavioral activation and evoked accumbens DA release at early withdrawal. Moreover, no enhanced DA response to a subsequent ETOH challenge could be demonstrated in ETOH experienced animals 2 weeks after withdrawal, in spite of the observation of clear behavioral sensitization at this time point. These results suggest that, at least in the case of ethanol, sensitization of the DA mesolimbic system may not be necessary for the development of behavioral sensitization.

“…Behavioral sensitization refers to the progressive increase in the locomotor stimulant properties of a drug following chronic drug administration and is considered a long-term neuro adaptation important for the maintenance of drug dependence (Kalivas et al, 1998;Robinson and Berridge, 1993;Vanderschuren et al, 1999). Cocaine-induced sensitization occurs through the stimulation of D 1 receptors on cortical afferents to the VTA, which, in turn, induces glutamate release.…”

Section: Cocaine-induced Sensitizationmentioning

confidence: 99%

The Role of Acetylcholine in Cocaine Addiction

Williams

Adinoff²

2007

164

138

Central nervous system cholinergic neurons arise from several discrete sources, project to multiple brain regions, and exert specific effects on reward, learning, and memory. These processes are critical for the development and persistence of addictive disorders. Although other neurotransmitters, including dopamine, glutamate, and serotonin, have been the primary focus of drug research to date, a growing preclinical literature reveals a critical role of acetylcholine (ACh) in the experience and progression of drug use. This review will present and integrate the findings regarding the role of ACh in drug dependence, with a primary focus on cocaine and the muscarinic ACh system. Mesostriatal ACh appears to mediate reinforcement through its effect on reward, satiation, and aversion, and chronic cocaine administration produces neuroadaptive changes in the striatum. ACh is further involved in the acquisition of conditional associations that underlie cocaine self-administration and context-dependent sensitization, the acquisition of associations in conditioned learning, and drug procurement through its effects on arousal and attention. Long-term cocaine use may induce neuronal alterations in the brain that affect the ACh system and impair executive function, possibly contributing to the disruptions in decision making that characterize this population. These primarily preclinical studies suggest that ACh exerts a myriad of effects on the addictive process and that persistent changes to the ACh system following chronic drug use may exacerbate the risk of relapse during recovery. Ultimately, ACh modulation may be a potential target for pharmacological treatment interventions in cocaine-addicted subjects. However, the complicated neurocircuitry of the cholinergic system, the multiple ACh receptor subtypes, the confluence of excitatory and inhibitory ACh inputs, and the unique properties of the striatal cholinergic interneurons suggest that a precise target of cholinergic manipulation will be required to impact substance use in the clinical population.