An acute i.c.v. infusion of leptin has no effect on hypothalamic histamine and tele-methylhistamine contents in Wistar rats

Abstract

The actions of intracerebroventricularly (i.c.v.) infused leptin on food intake, body weight and hypothalamic contents of histamine and tele-methylhistamine, the main histamine metabolite in the mammalian brain, were studied in male Wistar rats. The effect of the histamine H 1 receptor blockade on leptin-induced anorexia was also examined. It was found that leptin at the dose of 10 μg i.c.v. reduced 24-h food intake by 48% as compared with the controls ( P<0.01). This leptin dose reduced feeding during 2–4 consecutive days. In spite of the marked changes in food consumption and body weight gain, leptin did not alter the hypothalamic contents of histamine and tele-methylhistamine. Furthermore, the blockade of histamine H 1 receptors by mepyramine did not attenuate the effect of leptin on feeding and body weight. The findings indicate that centrally administered leptin suppresses feeding and promotes weight loss through mechanisms that do not require the direct participation of the brain histaminergic neuron system.