Abstract: The experiments were performed on conscious rats immobilized by flaxedil. Spontaneous cell firings in the nucleus accumbens (A) were recorded with autofilled microelectrode. The average firing rate of the neurons in A was 4.9 spikes/s. The firing rate was markedly decreased by intraperitoneal administration of d1-tetrahydropalmatine (THP). The depression of the firing appeared 10 min and reached its peak 30 rain after injection. Pretreatment with pargyline, a monoamine oxidase inhibitor, antagonized the THP-induced depression of the firing.The present study suggests that the results of the electrophysiological investigation coincide with those of biochemical study of THP as a monoamine depletor. Therefore, THP may be considered as a reserpine-like compound.