Vasomotor response of cerebral blood vessels to dopamine and dopaminergic agonists

The vasomotor response of dopamine and dopaminergic agonists was studies on feline isolated middle cerebral arteries in vitro and pial arterioles in situ following microapplication. The action of various inhibitors was tested to define the receptors involved. The contractile response could be blocked by alpha-receptor as well as serotonin receptor antagonists. The mode of inhibition suggested that serotonin receptors rather than alpha-adrenoceptors mediated the dopamine-induced contraction. A dose-dependent dilation could be evoked by the dopaminergic agonists on actively contracting pial arteries in vitro and by apomorphine in situ. The relative potency for the agonists together with blocking experiments indicated that the vasodilation was mediated by specific dopamine receptors.