AJP - Heart and Circulatory Physiology, Vol 256, Issue 1 105-H110, Copyright © 1989 by American Physiological Society
Sympathetic outflow to resting muscles during static handgrip and postcontraction muscle ischemia
B. G. Wallin, R. G. Victor and A. L. Mark
Department of Clinical Neurophysiology, Sahlgren's Hospital, University of Goteborg, Sweden.
Simultaneous microneurographic recordings were made of muscle sympathetic
activity (MSA) in the radial and the peroneal nerves of seven healthy
subjects during 2-min static handgrip (30% of maximal voluntary
contraction) followed by 2 min of forearm ischemia induced by arterial
occlusion. At rest sympathetic burst frequency was similar in both nerves,
but relative burst strengths differed between the two neurograms,
suggesting that sympathetic outflows to arm and leg were not identical.
Both radial and peroneal MSA were unchanged during the first minute of
handgrip and increased to a similar degree during the second minute. Thus
previously reported differences in vascular resistance between forearm and
calf during static handgrip cannot be explained by differences in MSA to
arm and leg muscles. During forearm ischemia after handgrip, peroneal MSA
remained at the same level as during the second minute of handgrip but
there was a further increase of radial MSA. This shows that stimulation of
chemosensitive endings in forearm muscles induces differentiation of
sympathetic neural outflow to muscles in the leg and the contralateral arm.
