Responses of thoracolumbar spinal neurons to renal artery occlusion

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.