The effects of buspirone on the behaviour of control and stressed mice.

The effects of buspirone on the locomotor activity and behaviour in the plus-maze and hole-board tests were studied in control and small platform stressed mice. Small platform stress for 24 hours increased the locomotor activity of mice and induced anxiolytic-like effect in the plus-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 was greater in small platform stressed mice. In control mice buspirone in doses 2.0 and 4.0 mg/kg exerted anxiolytic effect in the plus-maze and 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 decrease in the number of head-dippings and rearings in the hole-board test. These data suggest that small platform stress induces a sensitization of mice to the motor depressant effect of buspirone. At the same time small platform stress induces hyposensitivity to the anxiolytic effect of buspirone. It is proposed that these changes might be due to alterations in the serotonergic transmission or to changes in the release of corticosterone.