Influence of stressors on the rewarding effects of alcohol in Wistar rats:: studies with alcohol deprivation and place conditioning

Rationale and objectives: Studies on laboratory animals have provided conflicting results regarding the actions of stressors on the rewarding effects of alcohol. In the present study, we first examined the effects of footshock or social defeat, given during deprivation, on the alcohol deprivation effect (ADE). We then tested the effects of stressors on place conditioning to alcohol, another technique used to measure drug reward. Methods: Male Wistar rats were trained to drink 10% alcohol in a 24 h access, free-choice design and received intermittent footshock or defeat 5 times during a 2-week alcohol deprivation period, followed by 2 weeks of free access to alcohol. There were three such cycles. In the place conditioning studies, animals received footshock, defeat, or no stress immediately prior to conditioning sessions where they received alcohol (0.6 or 1.0 g/kg, IP) or vehicle injections. Results: Alcohol intake of footshock-treated animals was significantly higher than that of controls following the first and second, but not the third period of alcohol deprivation and stress exposure. Defeat caused a smaller increase in alcohol intake that was significant only after the first deprivation and stress cycle. In the place conditioning studies, we found that either stressor blocked the place aversion induced by 1.0 g/kg alcohol. Conclusions: These results demonstrate that stressors can modify the rewarding and aversive properties of alcohol, measured using two different paradigms. Footshock and defeat produced transient, but significant increases in the magnitude of ADE, while exposure to either stressor reduced the aversive effects of a high dose of alcohol measured using the place conditioning paradigm.