Total body thermosensitivity and its spinal and supraspinal fractions in the conscious goose.

Abstract

1. Effects of general body cooling on heat production: an intravascular heat exchanger was used to alter total body temperature. Heat production increased with decreasing body temperature at an average rate of -12W/kg x degree C. The rate of rise was independent of air temperature. The threshold body temperature below which heat production rose was lower at higher air temperature. 2. Effects of spinal cord cooling: heat production increased with decreasing spinal temperature at an average rate of -0.3 W/kg x degree C. The rate of rise was not clearly affected by air temperature. The spinal threshold temperature was lower at warm ambient conditions. The results suggest that spinal thermosensitivity in the goose represents only a minor fraction of total body thermosensitivity. 3. Effects of head cooling: heat exchangers closing the carotid arteries were used to alter the temperature of the blood supplied to the head. Cooling increased heat production. When the thermosensitivity of the area, which was affected by heat exchanger, was calculated from the relationship between changes of heat production and brain temperature, values between -0.74 and -1.65 W/kg x degree C were obtained. Measurements of brain, spinal cord and head skin temperatures suggest that the thermosensitive structures which mediated the responses, were predominantly situated in the brain.