EFFECT OF ADRENAL MEDULLECTOMY ON RESPONSES IN HEAT-PRODUCTION, PLASMA-CATECHOLAMINES AND BODY-TEMPERATURE OF BURNED RATS TO CHANGES IN THETEMPERATURE OF THE HYPOTHALAMUS

Burn (B) and control (C) rats with and without adrenal medullectomy (A dx) 9-11 days postburn underwent warming and cooling of the preoptic a nterior hypothalamus (POAH) during calorimetry at 22 degrees and 28 de grees C ambient. Blood was drawn for catecholamine assay during each d isplacement of the POAH temperature (T-hy). The heat production (H-p) for the AdxB group at 22 degrees and 28 degrees C was not different fr om the H-p for the sham AdxB group (80 +/- 4 vs 86 +/- 8 at 22 degrees C, 58 +/- 8 vs 64 +/- 7 W/m(2) at 28 degrees C) in spite of there bei ng no detectable circulating epinephrine (E) for the AdxB groups. Cool ing of the POAH of the AdxB 22 degrees C group, however, did not induc e a further increment in H-p, in contrast to all other groups. T-hy de monstrated good significant negative linear correlation with H-p for a ll groups. The resulting slopes were not significantly different from one another indicating no difference in thermal sensitivity of the POA H between the groups. In four of eight groups plasma norepinephrine (N E) demonstrated positive correlation with H-p and in five of eight gro ups negative correlation with T-hy. Plasma E values did not correlate with H-p and demonstrated negative correlation with T-hy in two of fou r possible groups. These data show that postburn hypermetabolism is no t dependent on E in the rat and suggest that NE may be calorigenic in burned rats.