Vasodilatation by endothelium-derived nitric oxide as a major determinant of noradrenaline release.
In the anaesthetized rabbit, L-NG-monomethyl-arginine (L-NMMA), a specific inhibitor of nitric oxide (NO) formation, was used to assess the role of endothelium-derived NO in the regulation of haemodynamics and noradrenaline release (RNA). L-NMMA dose-dependently increased mean arterial pressure and total peripheral resistance (TPR), but decreased heart rate, cardiac output and RNA. The curvilinear relationship between RNA and TPR obtained for L-NMMA was virtually identical with that produced by phenylephrine, indicating that L-NMMA-induced decreases in RNA are mediated by the baroreflex. Since the maximum RNA inhibition by L-NMMA was 69%, the counterregulation against peripheral vasodilatation by endothelium-derived NO accounts for 69% of basal RNA.
Halbrügge
T
T
Department of Pharmacology, University of Würzburg, Federal Republic of Germany.
Lütsch
K
K
Thyen
A
A
Graefe
K H
KH
D000818:Animals; D001120:Arginine / Q000031:analogs & derivatives* / Q000494:pharmacology; D001794:Blood Pressure / Q000187:drug effects; D002302:Cardiac Output / Q000187:drug effects; D004730:Endothelium, Vascular / Q000502:physiology*; D005260:Female; D006339:Heart Rate / Q000187:drug effects; D006439:Hemodynamics / Q000187:drug effects*; D008297:Male; D009569:Nitric Oxide / Q000378:metabolism*; D009638:Norepinephrine / Q000378:metabolism*; D010656:Phenylephrine / Q000494:pharmacology; D011311:Pressoreceptors / Q000187:drug effects / Q000502:physiology; D011817:Rabbits; D014655:Vascular Resistance / Q000187:drug effects; D014664:Vasodilation / Q000187:drug effects / Q000502:physiology*; D019323:omega-N-Methylarginine
D010656:Phenylephrine; D019323:omega-N-Methylarginine; D009569:Nitric Oxide; D001120:Arginine; D009638:Norepinephrine