VASODILATOR COMPONENT IN SYMPATHETIC-NERVE ACTIVITY DESTINED FOR THE SKIN OF THE DORSAL FOOT OF MILDLY HEATED HUMANS

1. Skin sympathetic nerve activity (SSNA) was recorded in seven male s ubjects from the peroneal nerve by microneurography, and the temporal correspondence of spontaneously occurring SSNA bursts with vasodilatat ion and sweating responses on the dorsal foot was studied during a mil d body heating at rest. 2. Some SSNA bursts were followed by a sweat e xpulsion with a latency of 2.4+/-0.4s, and some bursts by a transient vasodilatation with a latency of 2.2+/-0.4s (means+/-S.D). SSNA bursts followed both by a sweat expulsion and by a vasodilatation response ( Type 1), those followed only by a sweat expulsion (Type 2) and those f ollowed only by a vasodilatation response (Type 3) were 70 %, 10 % and 1 % of the total bursts examined, respectively 3. For Type 1 bursts, there was a significant, but weak linear relationship among the burst amplitude, the amplitude of the corresponding vasodilatation and the a mplitude of the corresponding sa eat expulsion. 4. It was concluded th at SSNA contains vasodilatory activity which is synchronous with sudom otor nerve activity. The results suggest that such vasodilatory activi ty contributes to sustaining the sweat gland function by supplying suf ficient blood.