Pharmacological evaluation of minaprine dihydrochloride, a new psychotropic drug

Minaprine (3-[2-morpholino-ethlamino]-4-methyl-6-phenyl-pyridazine dihydrochloride; 30038CM; trade name in France: Cantor) is a new psychotropic drug. The therapeutic profile of minaprine differs from that of other known psychotropic agents; in man the drug antagonizes the "inhibitory syndrome" characterized by decreased spontaneous activity, reduction in basic drives, slowed thoughts, feelings of tiredness and social withdrawal. Preliminary clinical trials have indicated that minaprine may also be effective in certain depressive states. This finding prompted us to study the effects of minaprine in animal models for depression. Like most antidepressants minaprine antagonizes behavioral despair, but the effect exhibits a slow onset and maximal activity is reached 24 h after administration. Minaprine also antagonizes reserpine-induced ptosis, this effect has a rapid onset, and is long-lasting. In contrast, minaprine poorly antagonizes reserpine-induced hypothermia. Unlike most antidepressants minaprine does not potentiate yohimbine-induced lethality. Minaprine potently antagonizes prochlorperazine-induced catalepsy in rats and potentiates amphetamine-induced stereotyped behavior, suggesting that the drug may enhance dopaminergic transmission. Finally, minaprine does not antagonize either oxotremorine-induced tremors or physiostigmine-induced lethality. Taken together the results of the present study indicate that minaprine is active on certain, but not all, animal models for depression and suggest the drug may have a potential clinical utility in the treatment of human depressions.