Inhibition of prostaglandin synthesis reduces hyperthermic reactions induced by hypocretin-1/orexin A.

This experiment tested (i) the effect of orexin A injected into a lateral cerebral ventricle on sympathetic and thermogenic activity and (ii) the involvement of prostaglandins in these phenomena. The firing rates of the sympathetic nerves to interscapular brown adipose tissue (IBAT), along with IBAT and colonic temperatures and heart rate were monitored in urethane-anesthetized male Sprague-Dawley rats before and 6 h after an injection of orexin A (1.5 nmol) into the lateral cerebral ventricle. The same variables were monitored in rats with an intraperitoneal administration of lysine acetylsalicylate (100 mg/kg bw), an inhibitor of prostaglandins synthesis. The results show that orexin A increases the sympathetic firing rate, IBAT and colonic temperatures and heart rate. This increase is reduced by lysine acetylsalicylate. These findings suggest that orexin A affects sympathetic activity, which controls body temperature. Prostaglandins are involved in this control.