Cerebral circulation: effect of stimulation and blockade of dopamine receptors.

The effects of stimulation and blockade of dopaminergic receptors on cerebral blood flow and metabolism were investigated in 15 anesthetized baboons. The intravenous administration of apomorphine resulted in immediate, dose-dependent increases in cerebral blood flow (increased by 58% following 0.1 mg/kg apomorphine) which were always accompanied by increases in cerebral oxygen consumption (increased by 36% with 0.1 mg/kg) and glucose uptake (increased by 72% with 0.1 mg/kg). It is suggested that the primary action of apomorphine is on cerebral metabolism and secondarily on cerebral blood flow rather than directly on cerebral vascular smooth muscle. Pimozide, at doses that totally blocked apomorphine-induced increases, was without effect on cerebral blood flow and metabolism. The dilatatory response of the cerebral circulation to hypercapnia was preserved during dopamine-receptor blockade. The basal level of overall cerebral metabolism and hemispheric cerebral blood flow does not appear to be dependent to any large extent on the activity of the dopaminergic pathways in the central nervous system.