EFFECTS OF CHLORDIAZEPOXIDE, BUSPIRONE AND THE 5-HT(3) RECEPTOR ANTAGONIST, BRL-46470, ON THE BEHAVIOR OF ESTROUS AND DIESTRUS FEMALE MICE WHEN ENCOUNTERING MALE PARTNERS

Ethological procedures were employed to examine the differences in beh aviour between oestrous and dioestrous control mice, and to investigat e the changes to behavioural responsiveness in oestrous and dioestrous mice induced by treatment with the anxiolytic compounds, chlordiazepo xide (CDP, 21.5mg/1), buspirone (12.8mg/1) and the 5-HT3 receptor anta gonist, BRL 46470 (40,ug/1). Compounds were given in drinking fluid fo r 6-8 days prior to behavioural observations (average daily intake: CD P-5 mg/kg; buspirone-2.5 mg/kg; BRL 46470-10 mug/kg). Behaviour of the females was examined in the ''approach-avoidance'' situation of 5 min encounters with an unfamiliar male in a neutral cage. Oestrous contro ls spent more time in social investigation, sniffing of the substrate and scanning than dioestrous controls and spent less time in digging a nd exploration. Each of the anxiolytic compounds, CDP, buspirone and B RL 46470, significantly raised the duration of social investigation bo th in oestrous and dioestrous females. Each of these compounds also in creased the duration of ''digging'' by oestrous females, and duration of the social element ''investigate'' in dioestrous females. Effects o n the occurrence of other individual elements within each behavioural category depended on the anxiolytic compound administered and the stag e of the ovarian cycle at the time of testing. There were few signific ant differences between the behaviour of the male partners in each gro up. It is concluded that in this paradigm both oestrous and dioestrous females are sensitive to the enhancement of social investigation by a nxiolytic compounds and that the use of female mice in this test situa tion may provide a potentially useful method in drug screening.