N G-Monomethyl- l-arginine co-injection attenuates the thermogenic and hyperthermic effects of E 2 prostaglandin microinjection into the anterior hypothalamic preoptic area in rats

Abstract

Prostaglandin E 2 (PGE 2) microinjection (25 ng, 250 nl) into the preoptic area of the anterior hypothalamus (POAH) stimulated heat production in brown adipose tissue (BAT) and increased core temperature in urethane-anesthetized rats. These thermogenic and hyperthermic effects were attenuated by co-injection of N G-monomethyl- l-arginine (NMMA, 25 μg), a competitive inhibitor of nitric oxide (NO) production from l-arginine. Inclusion of l-arginine (50 μg), though not d-arginine (50μg) reversed the inhibitory effect of NMMA (25μg) on intra-POAH PGE 2-induced increases in interscapular BAT (IBAT) and core temperatures. Intra-POAH injection of NMMA (25 μg) or l-arginine (50 μg) alone had no effect on IBAT and core temperatures. The results suggest that the effect on thermoregulation induced by action of PGE 2 in the POAH is modulated by a local l-arginine-dependent and NMMA-sensitive NO-generating system.