INVOLVEMENT OF GABA(B) RECEPTOR SYSTEMS IN ACTION OF ANTIDEPRESSANTS - BACLOFEN BUT NOT BICUCULLINE ATTENUATES THE EFFECTS OF ANTIDEPRESSANTS ON THE FORCED SWIM TEST IN RATS

Involvement of GABAergic systems in action of antidepressants was exam ined in the forced swim test in rats. Rats were forced to swim in a cy linder for 15 min on day 1 and for 5 min on day 2. Desipramine, mianse rin and buspirone, administered after the 15-min swim session on day 1 and before the 5-min swim test on day 2, dose-dependently decreased t he duration of immobility in the swim test on day 2. Baclofen attenuat ed the decreased duration of immobility induced by desipramine, mianse rin and buspirone in the swim test, although baclofen did not affect t he duration of immobility when it was injected alone. Muscimol dose-de pendently decreased the duration of immobility in the swim test on day 2. Bicuculline antagonized the decreased duration of immobility induc ed by muscimol. However, bicuculline failed to antagonize the decrease d duration of immobility induced by desipramine, mianserin and buspiro ne. These results suggest that GABA(B) but not GABA(A) receptor system s may be involved in action of antidepressants.