Differentiated sympathetic neural control of the kidney.
Dibona, Gerald F., Linda L. Sawin, and Susan Y. Jones.
Department of Internal Medicine, University of Iowa College of
Medicine & Veterans Administration Medical Center, Iowa City, Iowa
52242
APStracts 3:0008R, 1996.
Anatomic and neurophysiological methods were used to identify
functionally specific subgroups of renal sympathetic nerve fibers.
The distribution of diameters of the predominating unmyelinated
fibers showed a major mode at 1.1 [mu] and a minor mode at 1.6 [mu].
The conduction velocity was 2.10 +/- 0.10 m/sec, consistent with
unmyelinated C fibers. Analysis of strength-duration relationships
during renal nerve stimulation showed that both rheobase and
chronaxie values for renal blood flow were greater than those for
urinary flow rate and were independent of stimulation frequency. This
difference suggests a higher stimulation threshold (smaller diameter)
for those renal nerve fibers involved in the renal blood flow
response (renal vasoconstriction) compared to that for the urinary
flow rate response (antidiuresis) to renal nerve stimulation. Single
renal units that responded to pre-ganglionic splanchnic nerve
stimulation were studied. Those with spontaneous activity (88 %)
responded to stimulation of arterial baroreceptors, arterial and
central chemoreceptors and peripheral thermoreceptors while those
which lacked spontaneous activity (12 %) responded only to
stimulation of peripheral thermoreceptors (known to produce renal
vasoconstriction). A minority population of single renal units has
been identified which, while renal vasoconstrictor, does not exhibit
other characteristic features of vasoconstrictor neurons (i.e.,
responsiveness to stimulation of arterial baroreceptors, arterial and
central chemoreceptors). These findings suggest the existence of
functionally specific subgroups of renal nerve fibers.
Received 17 July 1995; accepted in final form 19 December 1995.
APS Manuscript Number R443-5.
Article publication pending Am. J. Physiol. (Regulatory Integrative
Comp. Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 22 January 96