Lipolytic responses induced by intracerebroventricular administration of histamine in the rat.

Histamine (10-50 microgram) administered intraventricularly in conscious rats induced an increase in serum-free fatty acids. The maximum, significant increase appeared 30-60 min after administration. Histamine H1-receptor antagonists, mepyramine and chloropyramine, when injected 2 h prior to histamine, abolished considerably hyperlipaemic responses to histamine. H2-Receptor antagonists, metiamide and cimetidine, given i.c.v. only moderately diminished histamine-induced hyperlipaemia. Histamine injected i.c.v. also increased serum corticosterone levels considerably. This elevation was prevented significantly by the H1-receptor antagonist, mepyramine, but not by the H2-receptor blocker, cimetidine. It seems likely that histamine given i.c.v. induces lipolysis through the release of ACTH, one of the known lipid-mobilizing hormones. The central lipid-mobilizing mechanism after histamine depends more on activation of H1- than H2-receptors.