Investigating social housing: The effects of isolation on rodent ethanol consumption

Many animal studies investigating Alcohol Use Disorder isolate animals for weeks at a time for accuracy in measures of voluntary consumption. This practice is stressful for the animals, and may be a confound for examining other behaviours following ethanol exposure. For example, chronic isolation and ethanol consumption have been shown to affect anxiety and depression-indicating behaviours in rats, but these studies report ethanol only as affecting anxiety while housing animals individually during ethanol access. Social behaviour has also been shown to moderate ethanol consumption in rats, but this effect has not been tested during the intermittent ethanol access, only in the weeks beforehand. We therefore conducted an experiment applying the IATBCP procedure to rats that were either continuously isolated or pair-housed during ethanol-free periods, split using both male and female rats. The animals had intermittent ethanol access for eight weeks, and then were subsequently tested for anxiety and explorative behaviour using the Successive Alleys Test (SAT). Following this we conducted the Anticipatory Behaviour Paradigm (ABP) to measure the animals’ anticipation to food rewards. The isolated animals showed significantly higher ethanol consumption and preference compared to the paired animals, while the paired animals showed greater anticipation on the ABP. The female rats also consistently consumed significantly more ethanol than the males, and showed greater anticipation. We found no difference in perceived anxiety/exploration using the SAT between any of our three main conditions (housing, sex, drinker/control).

These results demonstrate that housing conditions affect both ethanol consumption and anticipatory behaviour in rats, and that paired housing during intermittent ethanol access should be considered by experimenters. Our results also stress the importance of studying both sexes in animal research and the limitations of current animal research procedures.