Effect of adrenal medullectomy on responses in heat production, plasma catecholamines and body temperature of burned rats to changes in the temperature of the hypothalamus

Burn (B) and control (C) rats with and without adrenal medullectomy (Adx) 9–11 days postburn underwent warming and cooling of the preoptic anterior hypothalamus (POAH) during calorimetry at 22° and 28° C ambient. Blood was drawn for catecholamine assay during each displacement of the POAH temperature (Thy). The heat production (Hp) for the AdxB group at 22° and 28° C was not different from the Hp for the sham AdxB group (80 ± 4 vs 86 ± 8 at 22° C, 58 ± 8 vs 64 ± 7 W/m2 at 28° C) in spite of there being no detectable circulating epinephrine (E) for the AdxB groups. Cooling of the POAH of the AdxB 22° C group, however, did not induce a further increment in Hp, in contract to all other groups. Thy demonstrated good significant negative linear correlation with Hp for all groups. The resulting slopes were not significantly different from one another, indicating no difference in thermal sensitivity of the POAH between the groups. In four of eight groups plasma norepinephrine (NE) demonstrated positive correlation with Hp and in five of eight groups negative correlation with Thy. Plasma E values did not correlate with Hp and demonstrated negative correlation with Thy in two of four possible groups. These data show that postburn hypermetabolism is not dependent on E in the rat and suggest that NE may be calorigenic in burned rats.