PMID: 6168864Sep 1, 1981Paper

Tyramine-induced contractions in the rabbit ear and basilar arteries

Journal of Cardiovascular Pharmacology
T J LeeC Su

Abstract

This study examined in vitro tyramine (TY)-induced contractions of the isolated ring segments of the rabbit basilar and ear arteries in relation to their sympathetic innervations. The TY dose--response relationship in the basilar artery was not affected by cocaine, chronic sympathectomy, or reserpine pretreatment. However, these treatments shifted the TY dose--response relationship in the ear arteries significantly to the right. These results indicate that the TY-induced contraction in the basilar artery is due solely to its direct stimulation of the postsynaptic alpha-receptors, but in the ear artery it is due both to its indirect [release of norepinephrine (NE)] and direct actions. The failure of TY to induce contraction in the basilar artery by the indirect mechanism is probably in part due to a wide synaptic cleft distance and the reported insensitivity of alpha-receptors of this artery. These results suggest that the endogenous NE releasable from the sympathetic nerve in the basilar artery is insufficient to bring about vasoconstriction. This is turn favors our previous hypothesis that transmural-nerve-stimulation (TNS)-induced constriction of this artery is to a transmitter other than NE. It further suggests that the func...Continue Reading

Citations

Oct 1, 1989·Journal of Cerebral Blood Flow and Metabolism : Official Journal of the International Society of Cerebral Blood Flow and Metabolism·F J Miao, T J Lee
Jun 1, 1982·Circulation Research·T J Lee
Jun 1, 1985·Journal of Autonomic Pharmacology·S Chiba, T Ito

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