THE EFFECTS OF BUSPIRONE ON THE BEHAVIOR OF CONTROL AND STRESSED MICE

The effects of buspirone on the locomotor activity and behaviour in th e plus-maze and hole-board tests were studied in control and small pla tform stressed mice. Small platform stress for 24 hours increased the locomotor activity of mice and induced anxiolytic-like effect in the p lus-maze and hole-board tests. Administration of buspirone either did not affect (2.0 and 4.0 mg/kg) or inhibited (8.0 mg/kg) locomotions in control animals. The inhibition of locomotor activity by buspirone wa s greater in small platform stressed mice. In control mice buspirone i n doses 2.0 and 4.0 mg/kg exerted anxiolytic effect in the plus-maze a nd hole board test that was reflected by an increase in the percentage of entries onto and the percentage of time spent on the open arms of the plus-maze and increased number of head-dippings in the hole-board test. In contrast, in small platform stressed mice, buspirone did not induce anxiolytic action in the plus-maze and hole-board tests at any dose tested. In doses 2.0 and 4.0 mg/kg buspirone produced a sedative effect that was reflected by a decrease in the total number of entries made onto the open and into the closed arms of the plus-maze and a de crease in the number of head-dippings and rearins in the hole-board te st. These data suggest that small platform stress induces a sensitizat ion of mice to the motor depressant effect of buspirone. At the same t ime small platform stress induces hyposensitivity to the anxiolytic ef fect of buspirone. It is proposed that these changes might be due to a lterations in the serotonergic transmission or to changes in the relea se of corticosterone.