BUSPIRONE INCREASES SOCIAL-INVESTIGATION IN PAIR-HOUSED MALE-MICE - COMPARISON WITH THE EFFECTS OF CHLORDIAZEPOXIDE

Effects of buspirone (1, 5 and 10 mg/kg, i.p.) on the behaviour of adu lt male CD1 mice have been compared with those of chlordiazepoxide (1, 4 and 8 mg/kg, i.p.). Commencing at 30 min after injection, the behav iour of each mouse was examined by ethological procedures during 5 min social encounters with an untreated partner in the animal's home cage and in the more aversive situation of an unfamiliar neutral cage. In both test environments, buspirone at 1 and 5 mg/kg and chlordiazepoxid e (CDP) at 1 and 4 mg/kg increased social investigation and some of it s constituent elements, while decreasing non-social activity and the e lement, ''explore'' (and for CDP, of ''scanning'' also). In both test environments, the increase of social investigation by buspirone and CD P was less marked at 10 and 8 mg/kg, respectively. For CDP, although n ot for buspirone, this effect was related to dose-dependent increases of immobility coupled with reductions of exploratory non-social activi ty and scanning below those occurring at the intermediate dose level. Buspirone at 5 mg/kg increased social investigation to a greater exten t in the home cage (P < 0.01) than in the unfamiliar neutral cage (P < 0.05), whereas CDP was approximately equipotent in the two test situa tions. In the neutral cage, buspirone at all dose levels showed an add itional effect of increasing the time spent by the mice in digging, wh ereas chlordiazepoxide dose-dependently increased aggression. These re sults indicate anxiolytic activity by both compounds after acute admin istration, and identify certain differences in the profile of their ot her effects on social behaviour.