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 c erebral ventricle on sympathetic and thermogenic activity and (ii) the invo lvement of prostaglandins in these phenomena. The firing rates of the sympa thetic nerves to interscapular brown adipose tissue (IBAT), along with MAT and colonic temperatures and heart rate were monitored in urethane-anesthet ized 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 mo nitored in rats with an intraperitoneal administration of lysine acetylsali cylate, (100 mg/kg bw), an inhibitor of prostaglandins synthesis. The resul ts show that orexin A increases the sympathetic firing rate, IBAT and colon ic temperatures and heart rate. This increase is reduced by lysine acetylsa licylate. These findings suggest that orexin A affects sympathetic activity , which controls body temperature. Prostaglandins are involved in this cont rol. (C) 2001 Elsevier Science B.V. All rights reserved.