Skin sympathetic nerve function during sleep--a study with effector responses

We investigated the effector-organ activities corresponding to skin sympathetic nerve activity (SSNA) during sleep in eight healthy adult volunteers. The following parameters of SSNA were recorded during night sleep: the spontaneous skin vasoconstriction and skin blood flow volume, by laser Doppler flowmetry; sweating, by the ventilated capsule method; and the galvanic skin response (GSR). Fluctuations of sweating and GSR were mainly observed on the dorsal side of the hand during night sleep. The frequency of GSR and sweat rate on the dorsal side of the hand were significantly lower during REM sleep than during NREM sleep. The frequency of spontaneous skin vasoconstriction was higher and blood flow was lower during REM sleep than during NREM sleep. These results indicate that sweating and blood flow in the skin are differentially regulated depending on the sleep stage. Our results also suggest that the sleep-regulating system is closely linked to thermoregulation, which is controlled by the sympathetic nervous system.