Nature of histamine receptors in the emetic chemoreceptor trigger zone.

1 The protective effects of the intracerebroventicular (i.c.v.) administration of the H1-receptor antagonist, mepyramine and the H2-receptor antagonists, burimamide and metiamide on centrally induced histamine-emesis were studied in unanaesthetized dogs. 2 The PD50 values of intraventricular mepyramine, burimamide and metiamide against the 100% emetic dose of histamine (3.0 mg i.c.v.) were found to be approximately 200 mug, 20 mug and 20 mug respectively. 3 Although burimamide (i.c.v. or i.v.) afforded protection against histamine-induced emesis, there was no protection against intravenous apomorphine-or oral copper sulphate-induced emesis. 4 The results suggest that both H1- and H2-histamine receptors in the emetic chemoreceptor trigger zone of the area postrema are concerned in histamine-induced emesis.