Potentiating effects of 5-hydroxytryptamine and histamine on nerve stimulation-induced contractions of the rabbit mesenteric artery.
Contractions of the rabbit mesenteric artery induced by transmural adrenergic nerve stimulation at a frequency of 8 Hz were augmented by 5-hydroxytryptamine (5-HT), quipazine, methysergide, tolazoline, histamine, angiotensin II and 4-aminopyridine. The potentiating effect of 5-HT was partly reduced by cyproheptadine and by prolonged treatment with methysergide. After treatment with a histamine H1-antagonist, chlorpheniramine, histamine failed to augment but contrarily inhibited the response. This inhibition was reversed after subsequent administration of an H2-antagonist, metiamide. These results indicate that H1- and H2-receptors mediate the potentiation and inhibition, respectively, and that the effect medicated by H1-receptors normally predominates. It seems unlikely that the potentiation by these agents is due to prevention of norepinephrine metabolism, augmentation of norepinephrine release or prostaglandin formation. It is suggested that 5-HT and histamine act on postjunctional 5-HT and histamine receptors, respectively, to modulate the transmitter effect and that norepinephrine, methysergide and tolazoline may also act through the 5-HT receptors.
D015761:4-Aminopyridine; D000631:Aminopyridines / Q000494:pharmacology; D000818:Animals; D004347:Drug Interactions; D004558:Electric Stimulation; D005260:Female; D006632:Histamine / Q000494:pharmacology*; D066298:In Vitro Techniques; D008297:Male; D008638:Mesenteric Arteries / Q000187:drug effects; D009119:Muscle Contraction / Q000187:drug effects*; D009131:Muscle, Smooth, Vascular / Q000187:drug effects*; D011817:Rabbits; D012701:Serotonin / Q000494:pharmacology*
D000631:Aminopyridines; D012701:Serotonin; D006632:Histamine; D015761:4-Aminopyridine