CYCLOOXYGENASE INHIBITORS DEPRESS NOREPINEPHRINE CONSTRICTION OF RAT ABDOMINAL, BUT NOT THORACIC, AORTA

Experiments were done on aortic rings (thoracic and abdominal) from yo ung and retired breeder Lewis and Sprague-Dawley male rats. Constricti on responses to norepinephrine, 5-hydroxytryptamine (5-HT), and prosta glandin F-2 alpha were done +/- the cyclooxygenase blockers, indometha cin or mefenamic acid. Indomethacin significantly depressed norepineph rine constriction in abdominal (but not thoracic) aorta of all groups. In additional studies of abdominal aorta from Lewis retired breeders, indomethacin and mefenamic acid depressed norepinephrine (but not 5-H T or prostaglandin F-2 alpha) constriction. Furthermore, indomethacin depressed norepinephrine constriction in vessels denuded of endothelia l cells. The thromboxane receptor antagonist SQ 29548 did not alter no repinephrine constriction. Thus, in rat abdominal aorta, norepinephrin e constriction is mediated by a constrictor prostanoid of vascular smo oth muscle origin that is not thromboxane A(2).