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 rate, and oxygen (O-2) consumption were monitored in urethane-anesthetized 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 administration of 500 ng prostaglandin E(1) (PGE(1)). The same variables were monitored in other rats with muscimol injection or PGE(1) administration alone. No drug was injected in control rats. The results show that muscimol injection reduces the increases in firing rate, T-IBAT, T-c, heart rate, O-2 consumption induced by PGE(1). These findings suggest that GABAergic tone in the posterior hypothalamus is important in the control of thermogenic changes induced by PGE(1).