Dopamine-sensitive cAMP generating system in rat extracerebral arteries

The effect of dopamine (DA) on the 3',5'-cyclic adenosine monophosphate (cAMP) generating system in rat extracerebral arteries was studied in order to identify DA receptors. The carotis interna and the basilar artery as well as the arteries of the circle of Willis were homogenized and centrifuged. This extracellular arterial preparation was used for studying the effect of DA, norepinephrine and of drugs interfering with alpha- and beta-adrenergic as well as with dopaminergic receptors on cAMP production. DA increased the concentration of cAMP. The DA-elicited increase of cAMP levels was inhibited by dopamine receptor blocking agents (phenothiazine derivatives and butyrophenones) but unaffected by alpha- or beta-adrenoceptor blocking drugs or by the ergot-like DA agonist bromocriptine, or by sulpiride. The findings appear to be indicative of the existence of only D1 receptors within the blood vessels studied.