Effects of ethanol on behaviour of aggressive mice from two different strains: a comparison of simple and complex behavioural assessments.

The effects of acutely administered ethanol (0, 0.5, 1.0 and 2.0 g/kg IP) were studied in two strains of aggressively-rated, individually-housed male mice in encounters with non-drugged "standard opponents." Behaviour was quantified using both a complex ethological analysis of frequency of occurrence of acts and postures, and a more simplified analysis of time spent in 4 broad behavioural categories (non-social, social/sexual, aggressive and timid/defensive). The simplified analysis failed to reveal certain trends that were detected by the more complex analysis. The principal effects of alcohol on behaviour were a dose-dependent suppression of aggressive activities (with no evidence of a biphasic effect), an increase in timid/defensive behaviours, and changes in many non-social and social/sexual acts and postures. There were no qualitative inter-strain differences, but Swiss mice were markedly more sensitive to the drug than TO mice, particularly in their non-social, aggressive and timid-defensive behaviours. Strain differences in blood alcohol levels were only apparent at the lowest dose.