Effects of Activation of TRPM8 Ion Channels on Thermoregulatory Reactions in Cooling

Abstract

Animal experiments were performed to study the effects of activation of cold- and menthol-sensitive TRPM8 receptors by menthol on thermoregulatory parameters in thermoneutral conditions and on cooling. Total oxygen consumption was measured, along with expiration of carbon dioxide, the respiratory coefficient, the skin vessel constriction reaction, and contractile muscle activity. Application of menthol in thermoneutral conditions led to increased oxygen consumption and a decrease in the respiratory coefficient which, in the absence of shivering, provides evidence of increased non-contractile thermogenesis and lipolysis. Cooling on the background of activation of the TRPM8 receptor was characterized by decreases in the thresholds of all thermoregulatory reactions with no change in their initiation sequence, along with increases in the metabolic components of emergency thermogenesis, leading to improved maintenance of deep body temperature when environmental cold acts on the body. These results provide evidence for a contribution of TRPM8 ion channels to increased activation of thermoreceptor structures generating afferent signals involved in maintaining metabolism in thermoneutral conditions and forming the structure of the efferent response of the body to cold.