Role of endothelium and vasoconstrictor prostanoids in norepinephrine-induced vasoconstriction in isolated rat common carotid arteries.

We investigated the role of endothelium and vasoconstrictor prostanoids in the norepinephrine (NE)-induced vasoconstriction of isolated rat common carotid arteries (CCAs). Isolated CCAs were cannulated with stainless steel cannulae by the cannula inserting method. NE was administered intra- or extraluminally by a single microinjection. For denudation of endothelium, the intimal surface was gently rubbed with a cotton pellet. NE produced dose-related vasoconstricting responses in isolated arteries with intact endothelium. These responses were attenuated by pretreatment with denudation, OKY046, a thromboxane A2 synthesis inhibitor or indomethacin. The residual responses after denudation were further blocked by OKY046 or indomethacin. All NE-induced responses were blocked by a single injection of prazosin. There were no significant differences in responses between intra- and extraluminal administration of NE. These results show that most vasoconstriction induced by NE via alpha1-adrenoceptors in CCAs is dependent on vasoconstrictor prostanoids distributed both in endothelium and vascular smooth muscle.