The reversal by metoclopramide of apomorphine-induced inhibition of responses to stimulation of the cardioaccelerator nerves in the cat.
The effect of metoclopramide on presynaptic dopamine receptors was investigated in the cat cardioaccelerator nerve preparation. Metoclopramide, a substituted benzamide derivative, antagonized inhibitory action of apomorphine on positive chronotropic responses induced by sympathetic nerve stimulation in cat hearts, in vivo. Neither phentolamine, an alpha-adrenergic blocking agent, nor indomethacin a prostaglandin synthesis inhibitor, antagonized the effect of apomorphine. Apomorphine did not alter the positive chronotropic effects of intravenously administered noradrenaline. Metoclopramide potentiated stimulation-induced positive chronotropic responses. These results suggest that metoclopramide blocks the presynaptic dopamine receptors at the cat heart.
D000818:Animals; D001058:Apomorphine / Q000037:antagonists & inhibitors*; D002415:Cats; D004558:Electric Stimulation; D005260:Female; D006321:Heart / Q000294:innervation*; D006339:Heart Rate / Q000187:drug effects*; D007213:Indomethacin / Q000494:pharmacology; D008297:Male; D008787:Metoclopramide / Q000494:pharmacology*; D009638:Norepinephrine / Q000494:pharmacology; D010646:Phentolamine / Q000494:pharmacology; D011954:Receptors, Dopamine / Q000187:drug effects*; D013564:Sympathetic Nervous System / Q000187:drug effects
D011954:Receptors, Dopamine; D008787:Metoclopramide; D001058:Apomorphine; D009638:Norepinephrine; D007213:Indomethacin; D010646:Phentolamine