Social status and voluntary alcohol consumption in mice: interaction with stress

Abstract

Dominant rats are found to consume less alcohol than their subordinate cage-mates. It is unclear whether the difference is due to dominant, aggressive animals consuming low levels of alcohol or whether social stress increases alcohol intake in subordinate animals. The present study investigated alcohol drinking patterns in aggressive alpha mice, their fight-stressed submissive cage-mates and non-fighting control mice before and after the establishment of social hierarchies. The results revealed that both moderately and severely fight-stressed submissive mice showed increased consumption of 5% alcohol, expressed as g/kg, but only severely wounded submissive mice showed increased alcohol preference over total fluid consumption, as compared with alpha mice. The difference in alcohol consumption was not seen prior to the establishment of submissive and alpha status, indicating that the submissive mice increased their alcohol consumption only after experiencing fight-stress. The amount of alcohol consumed did not differ between alpha and non-fighting control mice. To further investigate the possible connection between alcohol intake and aggressivity, the mice were studied in the resident-intruder test before group-housing. The results failed to show a consistent pattern of correlations between the time spent in aggression in this test and subsequent alcohol intake measures. The data indicate that severe fight-stress increases alcohol consumption in mice. Alcohol intake of aggressive, dominant alpha mice is not significantly altered, as compared with non-fighting animals. Furthermore, the level of aggressiveness prior to the establishment of social status does not directly affect alcohol consumption. These results suggest that aggression and dominance are not critical in determining alcohol intake patterns, whereas being a target of severe social and physical stress significantly elevates alcohol consumption in mice.