Effects of sub-chronic treatment with chlordiazepoxide, buspirone and the 5-HT3 receptor antagonist, BRL 46470, on the social behaviour of mice

Chlordiazepoxide (21.5 mg/l; 5 mg/kg daily), buspirone (12.8 g/l; 3.4 mg/kg daily) and the 5-HT3 receptor antagonist, BRL 46470, (40 micrograms/l; 10 micrograms/kg daily) were each given in the drinking fluid for 12-14 days to adult male CD1 mice. Controls received tap water. Effects of the treatments on behaviour during 5 min social encounters with untreated partners were examined by ethological procedures in an aversive and less aversive situation, an unfamiliar neutral cage and the home cage. In the neutral cage all compounds increased the occurrence of the social act, "nose" and enhanced digging of the unfamiliar sawdust, at the expense of exploration. In the home cage, all compounds increased social investigation and reduced non-social activity. The drug BRL 46470 evoked more marked effects on behaviour than did buspirone or chlordiazepoxide and in the neutral cage it enhanced some acts of aggression. These results show that all compounds increased reactivity to normal social and environmental stimuli, in addition to their anxiolytic profile of behavioural effects.