This study will investigate the hypothesis that the hypermetabolic response (HMR) following burn injury is a thermoregulatory response, under central nervous system (CNS) control, to maintain body temperature (TB) in response to increments in the rates of evaporative and radiational heat loss occurring largely through the burn wound, and that changes in catecholamine metabolism represent a secondary response necessary to achieve maximum increase in heat production (Hp).
Specific aims i nclude: 1) establish the essentiality of the CNS thermoregulator in the production and maintenance of the HMR to burn injury, 2) evaluate the role of the adrenal medulla, sympathetic ganglia, and catecholamines as essential mediators of the HMR, 3) explore the possibility of increased thermogenic sensitivity of burned rats to norepinephrine (NE), similar to that seen with cold adaptation, and 4) determine the role of the burn wound in the afferent arc of the HMR. Responses in Hp, TB hypothalamic temperature (Thy), stored heat, partitioned heat loss, urinary excretion rates of NE and epinephrine (E), and plasma concentrations of NE and E will be measured and correlated with combinations of the following experimental interventions: a) lesioning of the preoptic anterior hypothalamus (POAH), b) no POAH lesion but implantation of the POAH with thermodes and sequential displacement of Thy, c) 35% BSA scald burn, d) adrenal demedullation, e) sympathetic blockade, f) intra- venous administration of E or NE, g) cold stress at 22 degrees C, h) early and delayed burn wound excision and closure with allograft or Biobrane. These studies should establish in the rat, the importance of an intact CNS temperature regulator in the production and maintenance of the HMR following burn injury, and quantitate the role of catecholamines and the adrenal medulla as effectors of the HMR. The wound excision and closure studies will demonstrate the effect of early and delayed eliminations of the burn wound on the interrelationship of the neurohormonal and HMR to burn injury. These results could produce a working model for the study and control of energy metabolism in burned man.
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