Blockade of neuronal tryptamine receptors by metoclopramide.
Metoclopramide (0.13, 0.51, 2.0 and 8.1 X 10(-6) M) caused parallel, rightward, shifts in the dose response curves to 5-HT on the isolated rabbit heart. A significant straight line relationship was found between log (5-HT dr--1) and log [metoclopramide] (molar) with a slope of 1.08 +/- 0.13 and giving a pA2 value of 7.20. Metoclopramide did not significantly alter responses to noradrenaline and was 575 times less effective as an inhibitor of DMPP than of 5-HT. The results indicate that metoclopramide is a potent, surmountable and selective antagonist of tryptamine receptors on rabbit cardiac sympathetic nerves.
D000818:Animals; D004246:Dimethylphenylpiperazinium Iodide / Q000494:pharmacology; D005260:Female; D006321:Heart / Q000294:innervation; D006339:Heart Rate / Q000187:drug effects; D066298:In Vitro Techniques; D008297:Male; D008787:Metoclopramide / Q000494:pharmacology*; D009200:Myocardial Contraction / Q000187:drug effects; D009474:Neurons / Q000187:drug effects; D011817:Rabbits; D011985:Receptors, Serotonin / Q000187:drug effects*; D012701:Serotonin / Q000494:pharmacology; D013564:Sympathetic Nervous System / Q000187:drug effects*
D011985:Receptors, Serotonin; D012701:Serotonin; D004246:Dimethylphenylpiperazinium Iodide; D008787:Metoclopramide