Effects of spinal cord temperature on the generation and transmission of temperature signals in the goat.

A series of 38 experiments were performed in five conscious goats at air temperatures of +20 degrees C or +30 degrees C to see whether a temperature dependence of spinal cord signal transmission affects the relationships between body temperature and metabolic rate (MR) or respiratory evaporative heat loss (REHL). Prior to the experiments the animals received peridural thermodes to clamp the spinal cord temperature by perfusion temperatures of 31 degrees C, 38 degrees C or 43 degrees C (45 degrees C), carotid loops to clamp the brain temperature at 39 degrees C or 39.5 degrees C, and arteriovenous shunts to alter the trunk temperature and to determine thresholds and slopes of MR and REHL over trunk temperature. The trunk temperature thresholds, at which MR and REHL increased, were inversely related to the spinal cord temperature, thereby confirming previous observations on the generation of specific spinal temperature signals. The slopes at which MR rose below the threshold, increased with decreasing spinal cord temperature. The slopes of REHL over trunk temperature were independent of spinal cord temperature. Both observations are at variance with previously observed temperature effects on hypothalamic signal transmission and imply that temperature-dependent signal transmission at the spinal level cannot account for nonlinear interaction of various body temperatures in the control of MR and REHL.