The effects of psychotropic drugs on THC-induced long-lasting muricide were investigated in rats. Changes in open field activity (ambulation and rearing) of the rat were concurrently assessed as an index of behavioral toxicity. Imipramine-like antidepressants, atropine, and antiparkinsonism drugs exhibited a selective inhibitory activity on muricide, whereas the effects of neuroleptics, pentobarbital, diazepam, and methamphetamine were nonspecific. It is also suggested that cholinergic, catecholaminergic, and serotonergic mechanisms are involved in THC-induced muricide. This type of induced muricide appears to be a useful experimental model particularly suitable for the evaluation of antidepressants in correlation with brain amine dynamics.