[Clinical application of skin sympathetic nerve activity]

Skin sympathetic nerve activity (SSNA) is microneurographically recorded from the skin nerve fascicle in the peripheral nerves. It is characterized by the following features: 1) irregular, pulse asynchronous, burst activity with respiratory variation, 2) burst activity followed by vasoconstriction and/or sweating, 3) elicited by mental stress and arousal stimuli, e.g., sound, pain, electric stimulation, 4) burst with longer duration as compared with sympathetic outflow to muscles, and 5) burst activity following sudden inspiratory action. It comprises vasoconstrictor (VC) and sudomotor(SM) activity, as well as vasodilator (VD) activity. VC and SM discharge independently, whereas VD is the same activity with different neurotransmission. The VC and SM are differentiated by effector response, e.g., laser Doppler flowmetry and skin potential changes. SSNA function in thermoregulation in the human body; however it is also elicited by mental stress. SSNA is the lowest at thermoneutral ambient temperature (approximately 27 degrees C), and is enhanced in the pressence of ambient warm and cool air. The burst amplitude is well-correlated to both skin blood flow reduction rate or sweat rate change. The clinical application of SSNA comprises the following: 1) clarification of sweating phenomenon, 2) clarification and diagnosis of anhidrosis, 3) clarification and diagnosis of hyperhidrosis, 4) clarification of thermoregulatory function and diagnosis of thermoregulatory disorder, 5) clarification of pathophysiology and diagnosis of vascular diseases, e.g., Raynaud and Buerger diseases. 6) clarification of the relation between cognitive function and SSNA and 7) determination of pharmacological effect attributable to change in neuroeffector responses.