Impromidine-induced hypothermia in rats: effect of cimetidine and mianserine.

Impromidine, a highly potent histamine H2-receptor agonist, given i.v. at doses of 3.1-62 nmole, induced a dose-dependent hypothermia in the rat with a maximal effect after 15 min. Cimetidine, an H2-receptor antagonist, having no effect when administered alone, antagonized the hypothermic action of impromidine. Two antiserotoninergic agents, p-chlorophenylalanine and metergoline, and chronic treatment with an antidepressant mianserine reduced the impromidine-induced hypothermia. It is suggested that the impromidine-induced hypothermia is an H2-receptor-mediated phenomenon, and the antagonizing effect of mianserine is related to serotonin receptor blocking activity of the drug rather than to its direct H2-receptor antagonism.