An ethological study of the effects of buspirone and the 5-HT3 receptor antagonist, BRL 43694 (granisetron) on behaviour during social interactions in female and male mice.

Buspirone (12.8 mg/l; 2.3-2.6 mg/kg daily) and the 5-HT3 receptor antagonist, BRL 43694 (granisetron) (40 micrograms/l; 10 micrograms/kg daily), were each given in drinking fluid to male and female DBA/2 mice for 5-10 days. Controls received tap water. Effects on behaviour were examined by ethological procedures during 5 min encounters with unfamiliar BKW partners. One group of DBA/2 males acted as intruders in a resident-intruder paradigm and another group encountered oestrous females in a neutral cage. The DBA/2 females each encountered a group-housed male in a neutral cage. Both buspirone and BRL 43694 decreased flight in females and increased the duration of their active social investigation. In females, BRL 43694 also reduced the occurrence of "scan" and prolonged the bout length of exploration. In male mice, buspirone increased social investigation, including the specific elements "sniff" and "follow" in encounters with female partners, but its only effect on behaviour during encounters with isolated resident males, was to decrease duration of the element, "attend". In males, BRL 43694 did not significantly affect behaviour in heterosexual encounters and had only a slight effect on behaviour during encounters with resident males, decreasing the occurrence of "eat". Overall, these results suggest that records of effects of drugs on flight responses of female mice, in encounters with male partners, may provide a sensitive index of the anxiolytic profile of novel compounds.