Reinstatement of Alcohol-Seeking Behavior by Drug-Associated Discriminative Stimuli after Prolonged Extinction in the Rat

Clinical observations suggest that stimuli associated with the availability or consumption of ethanol can evoke subjective feelings of craving and trigger episodes of relapse in abstinent alcoholics. To study the motivational significance of alcohol-related environmental cues experimentally, the effects of discriminative stimuli previously predictive of alcohol availability on the reinstatement of ethanol-seeking behavior were examined. Wistar rats were trained to lever-press for 10% (w/v) ethanol or water in the presence of distinct auditory cues. The rats were then subjected to an extinction phase where lever presses had no scheduled consequences. After extinction, the animals were exposed to the respective auditory cues without the availability of ethanol or water. Neither the ethanol (SA+) nor water-associated (SA−) auditory cue increased responding over extinction levels. In contrast, subsequent presentation of an olfactory cue associated with ethanol (SO+), but not a water-associated (SO−) cue significantly reinstated lever pressing behavior in the absence of the primary reinforcer. Moreover, responding elicited by the concurrent presentation of the SO+ and SA+ was selectively attenuated by the opiate antagonist naltrexone (0.25 mg/kg; sc). The results suggest that ethanol-associated cues can reinstate extinguished ethanol-seeking behavior in rats, but that the efficacy of these stimuli may be modality-specific. In addition, the present procedures may be useful for studying neurobiological mechanisms of alcohol-seeking behavior and relapse.