Background: In a preceding study, we reported that ethanol (EtOH) consumption during periadolescence in alcohol-preferring (P) rats produced significant effects on the acquisition, extinction, Pavlovian spontaneous recovery (PSR), and reacquisition of operant self-administration of EtOH. The objective of the present study was to determine if EtOH consumption during adulthood produced similar effects on subsequent operant behaviors.
Methods: Adult female P rats (>135 days of age) were given 24 hr free-choice access to 15% EtOH for 30 days or were similarly housed and received water only. After a 15 day period of no EtOH access and without any prior training, adult alcohol drinking and adult alcohol-naïve rats were placed in standard two-lever (15% EtOH and water) chambers to examine acquisition of EtOH self-administration. After stable responding was established on a concurrent fixed ratio (FR) 5 FR1 schedule for EtOH versus water, the P rats underwent extinction training for nine sessions. After extinction and a 2 week home cage period (with no operant sessions or access to EtOH), rats were returned to the operant chambers in the absence of reward for seven consecutive sessions to test for PSR. After PSR testing, animals were maintained in their home cage for a week, before being reintroduced to the operant chambers and allowed to respond for EtOH and water.
Results: Both the adult alcohol-drinking and adult alcohol-naïve groups rapidly acquired EtOH self-administration, expressed a pronounced PSR, which was augmented by EtOH priming and the presence of a discriminative stimulus (odor cue), and increased responding when EtOH was reinstated. Adult pre-exposure to EtOH did not alter any of the operant measures.
Conclusions: The results of this study suggest that, unlike the results with EtOH pre-exposure during periadolescence, chronic alcohol drinking by P rats in adulthood did not produce sufficient long-lasting changes in neuronal function to alter subsequent operant acquisition of alcohol self-administration, alcohol relapse, or alcohol-seeking behavior.