Studies on the central effects of bulbocapnine.

Abstract

In the present investigation the central effects of bulbocapnine were studied. In mice and rats, the antagonism and synergism on the part of various substances on bulbocapnine catalepsy were investigated, together with the influence of the drug on the EEG in animals with chronically implanted electrodes. In mice and rats, three types of drugs proved to be effective in attenuating the bulbocapnine-induced catalepsy: antihistaminics (diphenhydramine, promethazine), antiparkinsonians (amantadine, trihexyphenidyl), and antidepressives (imipramine). Potentiation in both intensity and duration of catalepsy was noted after administration of l-DOPA and 5-HTP. In rabbits, all the components of the cataleptic syndrome were much less marked than in the other animal species. Cats proved to be the most sensitive animal, the smallest effective dose of bulbocapnine being 5 mg/kg, s.c. A biphasic effect of bulbocapnine was demonstrated in the experiments involving concomitant observations of EEG and behavior. In none of the animal species used were significant alterations of the cerebral electrical activity observed during the cataleptic state. In mice and rats, spikes appeared in the EEG only after the onset of immobility and they anticipated the excitatory phase. Some of the described effects are interpreted as the results of an influence of the alkaloid on the central catecholaminergic system.