Location of vascular alpha 2-adrenoceptors in man.
To determine whether vascular postsynaptic alpha 2-adrenoceptors are innervated by sympathetic nerves in man, normal volunteers were infused for 90 min with angiotensin II (A II) and the alpha 2-adrenoceptor agonist alpha-methylnoradrenaline (MNA) in a double-blind cross-over study. Whilst systolic blood pressure returned to baseline within 5 min of terminating the A II infusion it remained elevated 40 min after stopping MNA. The prolongation of the pressor response to MNA, a substrate for neuronal uptake, was probably due to activation of alpha 2-adrenoceptors by MNA re-released from contiguous sympathetic nerve endings. The proximity of alpha 2-adrenoceptors to sympathetic nerve terminals suggests that they could contribute to blood pressure regulation in man.
D000328:Adult; D000804:Angiotensin II / Q000494:pharmacology; D001794:Blood Pressure / Q000187:drug effects; D001808:Blood Vessels / Q000294:innervation*; D006801:Humans; D008297:Male; D009411:Nerve Endings / Q000032:analysis; D008771:Nordefrin / Q000097:blood; D009638:Norepinephrine / Q000097:blood; D011942:Receptors, Adrenergic, alpha / Q000032:analysis*; D013564:Sympathetic Nervous System / Q000187:drug effects; D013997:Time Factors
D011942:Receptors, Adrenergic, alpha; D000804:Angiotensin II; D008771:Nordefrin; D009638:Norepinephrine