Skin sympathetic nerve activity and thermoregulatory control in humans

Abstract

Skin sympathetic nerve activity (SSNA) is microneurographically recorded from the skin nerve fascicle in the peripheral nerves with properties of an irregular, pulse asynchronous burst with respiratory variation, followed by sweating and/or vasoconstriction, elicited by mental stress and arousal stimuli. It comprises sudomotor and vasoconstrictor nerve activities as well as vasodilator ones. SSNA function in thermoregulation in humans, however, is also elicited by mental stress or cognition. SSNA is lowest at thermoneutral temperature and enhanced in the presence of ambient warm and cool air. Burst amplitude is well correlated to sweat rate change or skin blood flow reduction rate. The clinical application of SSNA comprises the following: (1) clarification of sweating events, (2) clarification and diagnosis of anhidrosis or hyperhidrosis, (3) clarification of thermoregulatory function and diagnosis of thermoregulatory disorder, (4) clarification of pathophysiology and diagnosis of vascular disorders, (5) clarification of the relationship between cognitive function and SSNA, and (6) determination of pharmacological effects attributable to change in neuroeffector responses. Lastly, SSNA’s significance as a feedforward thermoregulatory tool is discussed since SSNA contributes more to rapid thermoregulatory response than thermoregulation using convectional thermotransmission. Especially feedforward thermoregulatory sweating response is estimated to be highly phylogenetic than vasoconstrictive response.