AJP - Regulatory, Integrative and Comparative Physiology, Vol 262, Issue 5 834-R841, Copyright © 1992 by American Physiological Society
Age-dependent changes in afferent renal nerve activity in genetically hypertensive rats
N. G. Moss and A. B. Scoltock
Department of Physiology, University of North Carolina, Chapel Hill 27599-7545.
Multiunit and single-unit recordings of afferent renal nerve activity
(ARNA) were obtained in anesthetized spontaneously hypertensive rats (SHR)
and Wistar-Kyoto (WKY) rats between 35 and 150 days of age. Intrapelvic
backflow of urine at 20 mmHg excited ARNA at all ages in SHR (152 +/- 18%
above control) and WKY rats (262 +/- 24%). In SHR, complete renal ischemia
was more excitatory in rats older than 120 days (1,233 +/- 103%, n = 8)
than in younger SHR (317 +/- 28%, n = 42). Single-unit recordings showed
that this was related to the appearance of R1 chemoreceptors in older SHR
and coincided with a decline in the proportion of R2 chemoreceptors in the
renal nerves. Other chemoreceptive responses were identified in single
units that did not show complete R1 or R2 characteristics, some of which
showed responses consistent with a transformation process from R2 to R1
receptor type. R1 chemoreceptors were not present in WKY rats studied up to
150 days of age and, unlike SHR, the proportion of R2 chemoreceptors did
not decline with age. Accordingly, complete renal ischemia in WKY rats
caused a comparable excitation in multiunit ARNA at all ages (285 +/- 33%,
n = 43). Oral enalapril from weaning to 100 days of age prevented
hypertension in SHR but did not impair the responsiveness of ARNA to any
stimulus. In WKY rats, enalapril treatment for the same period resulted in
exaggerated ARNA response to renal ischemia (1,250 +/- 377% above
control).(ABSTRACT TRUNCATED AT 250 WORDS)
