Journal of Applied Physiology, Vol 68, Issue 1 71-75, Copyright © 1990 by American Physiological Society
Heat-induced finger vasoconstriction controlled by skin sympathetic nerve activity
T. Nagasaka, K. Hirata, T. Mano, S. Iwase and Y. Rossetti
Department of Physiology, School of Medicine, Kanazawa University, Japan.
Finger blood flow (BF) and skin sympathetic nerve activity (SSA) to the
glabrous side of the hand were measured during immersion of the hand in a
water bath in which temperature (Tw) was raised every 10 min by steps of 2
degrees C from 35 or 37 to 41 degrees C. The experiments were conducted
during the summer in rooms in which ambient temperature was 28-32 degrees C
or 35 degrees C. The nine healthy male subjects were wearing summer
clothes. Finger BF through vessels located deep in the skin was measured by
using laser-Doppler flowmetry (ALF-2100, Advance). With the use of a
tungsten microelectrode SSA was recorded directly from the median nerve at
the wrist or antecubital fossa of the tested arm. With finger vessels
already dilated at Tw of 35 or 37 degrees C, finger BF decreased, with a
concomitant increase in the SSA bursts as Tw rose to 39-41 degrees C. We
confirmed in one subject that anesthetic blockade of the median nerve at
the site proximal, but not distal, to the recording site blocked responses
to the step rise in Tw in the SSA bursts and in finger BF. From these
results we conclude that, with the subject in a warm state, blood vessels
of the finger respond to local heating with vasoconstriction, and this
finger vasoconstriction is evoked reflexively, largely through the
increased sympathetic outflow to the resistance vessels of the finger.
