Temperature sensitivity of skeletal muscle in the conscious goat

A method has been developed to test the hypothesis that the deep tissues of the legs, e.g., skeletal muscle and/or periosteum, contain thermosensitive elements feeding signals into the temperature-regulating system. Stainless steel thermodes of 10 to 12-mm diameter and 100 to 150-mm length were chronically implanted into the marrow spaces of both humeri and femora, all of which have wide cavities and thin walls. Perfusing the thermodes with water of 0 degree C altered the temperature of the deep muscle layers by several degrees. The animals were further equipped with intravascular heat exchangers, which served to keep general body temperature constant during periods of leg cooling. Eighty experiments were performed in a hot and dry environment. During the middle period of each experiment the legs were cooled by perfusing the thermodes with water of 0 degree C. This caused respiratory evaporative heat loss to decrease by 0.15-0.20 W/kg. The small but significant response occurred at constant general body temperature and is therefore indicative of a local effect of the cooling on deep thermosensitive elements in the legs themselves and a neural afferent transmission of temperature signals into the temperature-regulating system.