AJP - Regulatory, Integrative and Comparative Physiology, Vol 260, Issue 1 27-R31, Copyright © 1991 by American Physiological Society
Responses of spinoreticular cells to graded increases in renal venous pressure
W. S. Ammons
Department of Physiology, Thomas Jefferson University, Philadelphia, Pennsylvania 19107.
Previous work established that occlusion of the renal vein excites
spinoreticular tract (SRT) neurons of the cat. The present study was
designed to determine the relationship between renal vein pressure level
and SRT cell activity. Experiments were performed on 40 cats that were
anesthetized with alpha-chloralose. Sixty SRT neurons in the T12-L2
segments were tested for responses to a renal vein pressure (RVP) of 60
mmHg. Twenty-three cells responded with an increase in activity. Stimulus
response relationship for these cells were determined over the RVP range of
10-80 mmHg. RVP thresholds averaged 25 +/- 3 mmHg. Above this level greater
increases in RVP were associated with greater increases in neuronal
activity. At RVP of 80 mmHg cell activity increased from 4 +/- 2 to 21 +/-
5 spikes/s. Cells with both A delta- and C-fiber renal afferent inputs had
significantly greater responses and lower thresholds than cells with only A
delta input. Renal vein occlusion evoked increases in blood pressure. At a
renal vein pressure of 80 mmHg, pressor responses averaged 16 +/- 5 mmHg.
No significant changes in heart rate were observed. The results demonstrate
that SRT cells are capable of encoding the level of RVP. Such responses may
be important for grading of reflexes of renal origin that require
supraspinal circuitry.
