Differential drug effects on dopamine concentrations and rates of turnover in the median eminence, olfactory tubercle and corpus striatum.

Dopamine synthesis rates were determined in terminals of tuberoinfundibular, mesolimbic and nigrostriatal neuronal systems by observing the decline of dopamine contents in the median eminence, olfactory tubercle and corpus striatum after administration of alpha-methyltyrosine. In control (no drug treatment) animals the rate of synthesis of dopamine was greater in the median eminence than in the other two brain regions. Haloperidol increased and piribedil decreased dopamine turnover in the corpus striatum and olfactory tubercle, but not in the median eminence. Gamma-Butyrolactone increased dopamine concentrations in the olfactory tubercle and striatum without altering the concentration in the median eminence. Thus, the regulatory mechanisms governing the activity of central dopaminergic neurons in the tuberoinfundibular system appear to differ from those in the mesolimbic and nigrostriatal systems.