INJECTION OF MUSCIMOL IN THE POSTERIOR HYPOTHALAMUS REDUCES THE PGE(1)-HYPERTHERMIA IN THE RAT

The firing rate of the nerves innervating interscapular brown adipose tissue (IBAT), IBAT and colonic temperatures (T-IBAT and T-c), heart r ate, and oxygen (O-2) consumption were monitored in urethane-anestheti zed male Sprague-Dawley rats. These variables were measured for 40 min before (baseline values) and 40 min after a 56 ng muscimol injection in the posterior hypothalamus and an intracerebroventricular administr ation of 500 ng prostaglandin E(1) (PGE(1)). The same variables were m onitored in other rats with muscimol injection or PGE(1) administratio n alone. No drug was injected in control rats. The results show that m uscimol injection reduces the increases in firing rate, T-IBAT, T-c, h eart rate, O-2 consumption induced by PGE(1). These findings suggest t hat GABAergic tone in the posterior hypothalamus is important in the c ontrol of thermogenic changes induced by PGE(1).