The effect of baclofen on the locomotor activity of control and small-platform-stressed mice

The effect of boclofen on the locomotor activity of control and small-platf orm-stressed mice was studied. In the small platform technique, mice are fo rced to stay on small platforms (d = 3.5 cm) surrounded by water for 24 h. Small platform stress increased the locomotor activity of mice in the actom eter. Baclofen administered at doses of 0.25, 0.5 and 1.0 mg kg(-1) (i.p.) had no effect on the locomotor activity of control mice. In small-platform- stressed mice, the locomotor depressant effect of baclofen was pronounced, bring statistically significant at a dose of 1.0 mg kg(-1). These data sugg est that small platform stress induces hypersensitivity of mice to the moto r depressant effect of baclofen. On the basis of these data it could be pro posed that small platform stress induces changes in the function of GABA(B) receptors and that GABA(B) receptors participate in the behavioural change s caused by small platform stress. (C) 2000 Academic Press.