The conditioning of cocaine’s subjective actions with environmental stimuli could be

The conditioning of cocaine’s subjective actions with environmental stimuli could be a critical factor in long-lasting relapse risk associated with cocaine addiction. expression then were determined in two groups. One group was tested immediately after extinction whereas rats in the second group were confined to their home cages for an additional 4 months before testing. In both groups the cocaine SD but not the non-reward SD elicited strong recovery of responding and increased Fos Rabbit Polyclonal to Cyclin E1 (phospho-Thr395). immunoreactivity in the basolateral amygdala and medial prefrontal cortex (areas Cg1/Cg3). The response reinstatement and Fos expression induced by the cocaine SD were both reversed by selective dopamine D1 receptor antagonists. The undiminished efficacy of the cocaine SD to elicit drug-seeking behavior after 4 months of abstinence parallels the long-lasting nature of conditioned cue reactivity and cue-induced cocaine craving in humans and confirms a significant role of learning factors in the long-lasting addictive potential of cocaine. Moreover the results implicate D1-dependent neural mechanisms within the medial prefrontal cortex and basolateral amygdala as substrates for cocaine-seeking behavior elicited by cocaine-predictive environmental stimuli. The conditioning of cocaine’s pharmacological actions with discrete environmental stimuli has been implicated as a ML-3043 major factor in the abuse potential of this drug (1). Both retrospective (2) and controlled laboratory studies (3-5) show that such stimuli can evoke drug desire that may lead to the resumption of drug use in abstinent individuals. Drug-related stimuli may also elicit automatic responses that lead to drug-seeking behavior and relapse ML-3043 without the intervention of distinct feelings of craving (6 7 Learned responses to drug-related stimuli therefore represent a possibly critical element contributing to the chronic relapsing nature of cocaine and other drug addiction (8 9 Consistent with a role of learning factors in the initiation of drug-seeking behavior cocaine-related stimuli can elicit strong ML-3043 recovery of responding at a lever previously associated with i.v. cocaine infusions in animal models of relapse (10 11 However little information is available about the perseverance of the motivating actions of such stimuli over prolonged periods of abstinence and the neurobiological substrates mediating these effects. In humans relapse risk is typically greatest during the first 6 months of abstinence but may persist for substantially longer periods of time (1 8 12 Better understanding of the environmental conditions contributing to long-lasting vulnerability to relapse and the neurobiological basis of this phenomenon will be of substantial clinical benefit. In work that has begun to address this issue the efficacy of a cocaine-predictive discriminative stimulus to elicit responding at a previously active cocaine-paired lever was found to remain unaltered over 8 days of intermittent testing (11). These findings indicated that the behavioral actions of cocaine-related environmental stimuli are resistant to extinction despite repeated nonreinforced exposure to these cues. Here we have investigated the significance of drug-related environmental ML-3043 stimuli in enduring vulnerability to relapse by examining whether a drug-predictive stimulus retains its efficacy to induce cocaine-seeking behavior after long-term abstinence. Additionally to identify sites that may participate in the control ML-3043 of conditioned cocaine-seeking behavior the rats’ brains were examined for regions showing neural activation after exposure to the cocaine cue as measured by increased expression of Fos the protein product of the immediate-early gene c-fos (13 14 Lastly because of evidence that cue-induced cocaine craving in humans is associated with neural activation in dopamine-rich forebrain regions (4 5 15 and that cocaine cues increase dopamine release within these regions in rats (11) a third objective was to determine whether the behavioral effects of the cocaine-predictive stimulus and its effects on Fos expression ML-3043 are sensitive to pharmacological antagonism of dopamine neurotransmission. Materials and Methods Subjects. Male Wistar rats (Charles River Breeding Laboratories) weighing 250 g at the beginning of the experiment were used. Rats were housed in groups of two or three in a.