COMPARISON OF EFFECTS OF HALOPERIDOL ON DOPAMINE TURNOVER IN STRIATUM, OLFACTORY TUBERCLE AND MEDIAN-EMINENCE

Abstract

A sensitive radioenzymatic procedure was used to quantify haloperidol''s effects on dopamine concentrations and turnover rates in rat striatum, olfactory tubercle and median eminence, regions containing terminals of nigrostriatal, mesolimbic and tuberoinfundibular neurons, respectively. Haloperidol (2.5 mg/kg s.c.) did not alter the steady-state dopamine concentrations in any of these brain regions at any time. Haloperidol increased dopamine turnover in the striatum and olfactory tubercle 2 and 8 h after administration. The dopamine turnover rate was increased only in the median eminence 16 and 24 h after haloperidol administration, an effect which was blocked by hypophysectomy. Two other antipsychotic agents, clozapine and thioridazine increased dopamine turnover in the median eminence 16 h after the 1st of 2 injections. Evidence was provided for the existence of hormonal-neuronal feedback modulation of tuberoinfundibular dopaminergic neurons in contrast to the neuronal feedback modulation of nigrostriatal and mesolimbic neurons.