Effect of GABAergic drugs in the behavioral 'despair' test in rats

Aminooxyacetic acid (AOAA, 25 mg/kg i.p.), muscimol (2 mg/kg i.p.) and 4,5,6,7-tetrahydroisooxazol-[4,5-c]-pyridin-3-ol (THIP, 5 and 10 mg/kg s.c.), but not baclofen (10 mg/kg i.p.) administered three times (24, 5 and 1 h before the test) decreased the immobility time of rats in the behavioral 'despair' test. At these doses, AOAA, muscimol and THIP reduced motor activity. Muscimol (2 mg/kg) and THIP (5 and 10 mg/kg) exerted the antiimmobility effect even after single dosing 1 h before the test. Picrotoxin (1 and 2 mg/kg i.p.), but not bicuculline (2 mg/kg i.p.), prevented the effect of both muscimol and THIP in the behavioral 'despair' test.