Persistent suppression of ethanol self-administration by brief social stress in rats and increased startle response as index of withdrawal

Excessive alcohol drinking is often linked to the experience of stress, but experimental approaches using animal models of alcohol self-administration have had widely varying outcomes. The objective was to determine how daily exposure to brief, predictable social stress would change alcohol self-administration in rats in a daily limited access protocol. Male Long–Evans rats had either access to a 10% ethanol solution for 15 min in the home cage setting ( n=20) or were reinforced with 15% ethanol deliveries for every fifth lever press ( n=10). Subsequently, all rats were subjected to brief social stress for five consecutive days. Social stress consisted of attacks by an opponent for 5 min followed by exposure to threats while in a protective cage for 30 min. In both the home cage drinking and operant conditioning groups, social stress exposure significantly decreased alcohol intake or rate of alcohol reinforcements, respectively. When alcohol intake was scheduled immediately before social stress (i.e., 24 h after the previous social stress episode), a decrease was observed with a delay of 1 or 2 days. When alcohol intake was scheduled 4 h after stress, no changes in intake or alcohol reinforcements were observed. Animals that consumed a low dose of ethanol displayed less defensive behavior during social stress compared to water-drinking animals, and showed an increased startle reflex at 8 and 56 h after discontinuation of daily ethanol access. The current experimental protocols of social defeat stress reveal a transient suppression rather than a facilitation of alcohol consumption.