NG-monomethyl-L-arginine co-injection attenuates the thermogenic and hyperthermic effects of E2 prostaglandin microinjection into the anterior hypothalamic preoptic area in rats.

Prostaglandin E2 (PGE2) 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 NG-monomethyl-L-arginine (NMMA, 25 micrograms), a competitive inhibitor of nitric oxide (NO) production from L-arginine. Inclusion of L-arginine (50 micrograms), though not D-arginine (50 micrograms) reversed the inhibitory effect of NMMA (25 micrograms) on intra-POAH PGE2-induced increases in interscapular BAT (IBAT) and core temperatures. Intra-POAH injection of NMMA (25 micrograms) or L-arginine (50 micrograms) alone had no effect on IBAT and core temperatures. The results suggest that the effect on thermoregulation induced by action of PGE2 in the POAH is modulated by a local L-arginine-dependent and NMMA-sensitive NO-generating system.