HISTAMINE H(2)-RECEPTOR PLAYS ONLY A MINOR ROLE IN HISTAMINE-INDUCED WHEAL RESPONSE IN THE SQUIRREL-MONKEY AND GUINEA-PIG

We examined the contribution of the histamine H-2-receptor to the hist amine-induced wheal response in squirrel monkeys and guinea pigs. Intr adermal injection of histamine, 2-pyridylethylamine (a selective H-1-a gonist), and dimaprit (a selective H-2-agonist) dose-dependently induc ed the wheal response in squirrel monkeys and guinea pigs, although th e reaction to dimaprit was much weaker than that to the other agonists . Chlorpheniramine dose-dependently depressed the wheal response in sq uirrel monkeys and guinea pigs at doses of 0.03 - 1 mg/kg and 0.03 - 3 mg/kg, p.o., respectively. However, famotidine, ranitidine and cimeti dine had no effect at doses up to 30, 100 and 300 mg/kg, p.o. in guine a pigs and up to 1, 10 and 400 mg/kg, p.o. in squirrel monkeys, respec tively. Cimetidine (3 - 300 mg/kg, p.o.) dose-dependently potentiated the inhibitory effects of chlorpheniramine (0.1 mg/kg, p. o.) in guine a pigs, but had no effects in squirrel monkeys. Famotidine and ranitid ine did not alter the response to chlorpheniramine in either animal. T hese results suggest that the histamine H-2-receptor plays only a mino r role in the histamine-induced wheal response in squirrel monkeys and guinea pigs.