Histaminergic H1 and H2 excitatory receptors in the guinea pig uterus and taenia coli.

ABSTRACT

Histamine, 2-(2-pyridyl)ethylamine (PEA), a specific H1 receptor agonist, and 4-methylhistamine (4-MH), a specific H2 receptor agonist, produced a dose-dependent contraction of estrogen-primed guinea pig uterus and taenia coli. Mepyramine (10(-7) M), a specific H1 receptor antagonist, competitively blocked the responses to histamine and PEA in both the preparations. Metiamide (10(-6) M), a specific H2 receptor antagonist, inhibited the responses to histamine and 4-MH in the guinea pig uterus and taenia coli. Our data suggest the presence of both H1 and H2 receptors in the guinea pig uterus and taenia coli. Both receptors appear to be excitatory in nature.