AJP - Heart and Circulatory Physiology, Vol 256, Issue 6 1515-H1523, Copyright © 1989 by American Physiological Society
Responses of thoracolumbar spinal neurons to renal artery occlusion
W. S. Ammons and R. Sinha
Department of Physiology, Thomas Jefferson University, Philadelphia, Pennsylvania 19107.
Experiments were performed to examine responses of spinal neurons to
activation of renal chemoreceptors during renal artery occlusion (RAO). One
hundred twenty-two spinal neurons were studied in 33 cats that were
anesthetized with alpha-chloralose. Cells studied in the L2-T11 segments
were excited by electrical stimulation of the renal nerves and responded to
stimulation of somatic structures. RAO (90 s) excited 67 cells (55%).
Twenty-eight cells were excited at the onset of occlusion (from 5 +/- 1 to
27 +/- 5 spikes/s) and then either completely or partially adapted (ON
responses). Another 39 cells were excited at the onset of occlusion,
adapted to varying degrees, and then exhibited a second increase in
activity beginning 41 +/- 7 s into the occlusion period [onset-ischemic
(ON/IS) responses]. The secondary increase reached a peak of 15 +/- 2
spikes/s 65 s after occlusion. Among the responding cells, ON responses
were associated with cells receiving A delta only or with cells with A
delta- and C-fiber renal inputs. In contrast, 100% of cells with ON/IS
response received both A delta- and C-fiber inputs. Probability of finding
responding cells was greatest in the most rostral segments. We conclude
that ON responses to RAO are due to activation of mechanoreceptors in the
renal artery. ON/IS responses must have resulted from activation of
mechanoreceptors followed by activation of renal chemoreceptors in
association with development of renal ischemia. These data provide evidence
for activation of spinal neurons by RAO. These neurons may be important for
renal reflexes of chemoreceptor origin.
