The effect of morphine in rat small mesenteric arteries.
We investigated the effect of morphine in phenylephrine (PE)- or KCl-precontracted rat small mesenteric arteries. Morphine (10(-6)-10(-4) M) administration caused concentration-dependent relaxation responses in small mesenteric arteries precontracted by PE or KCl. Removal of endothelium did not significantly alter the relaxation responses to morphine. The relaxant responses to morphine were partially inhibited by pre-treatment of tissues with naloxone (NAL, 10(-5) M) for 20 min. The inhibitory effect of NAL on relaxant responses to morphine in PE- or KCl-precontracted arteries did not differ significantly between endothelium-intact and endothelium-denuded preparations. Incubation of endothelium-intact or endothelium-denuded arterial segments with NOS inhibitor N(omega)-nitro-L-arginine methyl ester (L-NAME, 10(-4) M) or cyclooxygenase (COX) inhibitor indomethacin (10(-5) M) or histamine H(1)-receptor blocker diphenhydramine (10(-6) M), for 20 min did not inhibit the relaxation responses to morphine. Small mesenteric arterial segment contractions induced by stepwise addition of calcium to high KCl solution with no calcium were almost completely inhibited by morphine. These findings suggested that morphine-induced relaxation responses in isolated rat small mesenteric arteries were neither dependent on endothelium nor blocked by NOS or COX inhibition but they rather seem to depend on an interaction of morphine with calcium influx pathways.
Ozdem
Sadi S
SS
Department of Pharmacology, Akdeniz University, Medical Faculty, 07070 Antalya, Turkey. sozdem@akdeniz.edu.tr
Batu
Ozlem
O
Tayfun
Fatma
F
Yalcin
Ozlem
O
Meiselman
Herbert J
HJ
Baskurt
Oguz K
OK
D000818:Animals; D002118:Calcium / Q000494:pharmacology; D004155:Diphenhydramine / Q000494:pharmacology; D004730:Endothelium, Vascular / Q000502:physiology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006634:Histamine H1 Antagonists / Q000494:pharmacology; D066298:In Vitro Techniques; D007213:Indomethacin / Q000494:pharmacology; D008297:Male; D008638:Mesenteric Arteries / Q000187:drug effects*; D009020:Morphine / Q000494:pharmacology*; D009131:Muscle, Smooth, Vascular / Q000187:drug effects*; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D009294:Narcotics / Q000494:pharmacology*; D009569:Nitric Oxide / Q000502:physiology; D010656:Phenylephrine / Q000494:pharmacology; D011451:Prostaglandin-Endoperoxide Synthases / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D014655:Vascular Resistance / Q000187:drug effects; D014662:Vasoconstrictor Agents / Q000494:pharmacology
D004791:Enzyme Inhibitors; D006634:Histamine H1 Antagonists; D009294:Narcotics; D014662:Vasoconstrictor Agents; D010656:Phenylephrine; D009569:Nitric Oxide; D009020:Morphine; D004155:Diphenhydramine; D011451:Prostaglandin-Endoperoxide Synthases; D002118:Calcium; D019331:NG-Nitroarginine Methyl Ester; D007213:Indomethacin