Tonic descending modulation of spinal neuronal responses to activation of renal receptors.
Experiments were conducted in anesthetized cats to determine if spinal neuronal responses to activation of renal receptors are tonically modulated by descending spinal pathways. Eighty-seven thoracolumbar spinal neurons with renal and somatic input were tested for responses to occlusion of the renal vein, renal artery, and ureter before, during, and after cooling the spinal cord rostral to the recording site. Cooling increased the number of neurons that responded as well as the magnitude of the responses to renal vein (RVO), renal artery (RAO), and ureteral occlusion (UO). RVO increased cell activity of 21 neurons from 12.5 +/- 2.7 to 31.7 +/- 6.0 spikes/s during cooling. UO increased cell activity of 24 neurons from 9.0 +/- 2.1 before cooling to 25.0 +/- 4.9 spikes/s during cooling. Cold block increased the magnitude of both types of responses to RAO that were due to mechanical deformation of the renal artery and prolonged renal ischemia. These data show that the majority of spinal neuronal responses to renal receptor stimulation are modulated by tonic inhibitory influences. Thus these results provide a mechanism by which the brain may control spinal circuitry that underlies reflexes of renal origin.
Standish
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A
Department of Physiology, Thomas Jefferson University, Philadelphia, Pennsylvania 19107.
Vizzard
M A
MA
Ammons
W S
WS
D000818:Animals; D002415:Cats; D002628:Chemoreceptor Cells / Q000502:physiology*; D003080:Cold Temperature; D003655:Decerebrate State; D004525:Efferent Pathways / Q000502:physiology; D004558:Electric Stimulation; D007668:Kidney / Q000294:innervation*; D008026:Ligation; D008465:Mechanoreceptors / Q000502:physiology*; D009407:Nerve Block; D009424:Nervous System Physiological Phenomena; D009474:Neurons / Q000502:physiology*; D012077:Renal Artery / Q000502:physiology; D012082:Renal Veins / Q000502:physiology; D013116:Spinal Cord / Q000166:cytology / Q000502:physiology*; D014513:Ureter / Q000502:physiology