[Diurnal fluctuations in the activity of the caudate nucleus and its sensitivity to psychotropic agents in cats].

Restraining function of the caudate nucleus in cats is less pronounced and amphetamine-induced stereotypy is more demonstrable at night time than at day time. Amphetamine reduces caudate activity also more markedly at night. Haloperidol, on the contrary, decreases more significantly the thresholds of arrest reaction induced by stimulation of the caudate nucleus and abolishes amphetamine-induced stereotypy at day time. The data obtained might be explained by more appreciable accumulation of nigro-strial dopamine by cats at dark time.