Central histaminergic stimulation of hyperlipemic response in rats under stress.

In rats subjected to a mild stress of immobilization histamine, the H1-receptor agonist 2-pyridylethylamine (PEA), and the H2-receptor agonists 4-methyl histamine (4-MeHA) and impromidine administered intracerebroventricularly (i.c.v.) 1 h prior to stress, intensified the stress-induced increase in serum free fatty acid (FFA) levels. Impromidine was far more potent than histamine and its agonists in increasing hyperlipemia in stressed rats. The hyperlipemic response to histamine was abolished by i.c.v. pretreatment of rats with mepyramine, a H1-receptor antagonist, but was unchanged in rats pretreated with cimetidine or metiamide, H2-receptor antagonists. The increase in serum FFA levels induced in stressed rats by PEA was abolished by mepyramine but the hyperlipemic responses to 4-MeHA and impromidine were not antagonized by cimetidine. These results suggest that central H1-receptor mediate the histamine-stimulated hyperlipemic response in stressed rats.