Pharmacologic studies on the mechanism of melatonin-induced vasorelaxation in rat aorta.
The influence of several classes of drugs on the melatonin-induced vasorelaxation of isolated rat aorta were examined. Melatonin caused a dose-dependent relaxation of precontracted (30 mM KCl) aorta. This relaxant response was blocked by preincubating vessels with antagonists of vasoactive intestinal peptide. Substance P antagonists did not alter the response to melatonin. Pretreatment of vessels with 6-hydroxydopamine, lidocaine, or tetrodotoxin antagonized the relaxant response to melatonin. On the other hand, pretreatment with atropine + propranolol did not alter the response to melatonin. These experiments suggest that melatonin may exert part of its vasoactive actions by an interaction with perivascular nerve terminals.
Weekley
L B
LB
Division of Comparative Medicine, University of Texas Southwestern Medical School, Dallas 75235-9037, USA.
D000818:Animals; D001013:Aorta, Thoracic / Q000187:drug effects*; D001285:Atropine / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D008012:Lidocaine / Q000494:pharmacology; D008297:Male; D008550:Melatonin / Q000494:pharmacology*; D009126:Muscle Relaxation / Q000187:drug effects / Q000502:physiology*; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013373:Substance P / Q000037:antagonists & inhibitors / Q000494:pharmacology; D013565:Sympatholytics / Q000494:pharmacology; D013779:Tetrodotoxin / Q000494:pharmacology; D014660:Vasoactive Intestinal Peptide / Q000037:antagonists & inhibitors / Q000494:pharmacology; D014661:Vasoconstriction; D014666:Vasomotor System / Q000187:drug effects
D013565:Sympatholytics; D013373:Substance P; D014660:Vasoactive Intestinal Peptide; D013779:Tetrodotoxin; D001285:Atropine; D008012:Lidocaine; D008550:Melatonin