Mc. Irigoyen et al., CHANGES OF RENAL SYMPATHETIC ACTIVITY IN ACUTE AND CHRONIC CONSCIOUS SINOAORTIC DENERVATED RATS, Hypertension, 26(6), 1995, pp. 1111-1116
The arterial pressure level attained in sinoaortic denervated depends
on the net effect of eliminating excitatory inhibitory influences (che
moreceptor and baroreceptor elimination, respectively). After sinoaort
ic denervation is completed, the hypertension usually observed within
the first few days is followed by normotension at the chronic stages.
In this work renal sympathetic nerve activity was measured in consciou
s, unrestrained rats 6 hours (acute) and 20 days (chronic) after sinoa
ortic denervation. Increased arterial pressure (154+/-10 versus 114+/-
3 mm Hg in controls) and renal sympathetic nerve activity (32+/-5 vers
us 13+/-2 bars per cycle in controls) with no changes in heart rate (4
04+/-17 vs 380+/-26 beats per minute) were observed in rats with acute
sinoaortic denervation. In rats with chronic sinoaortic denervation,
arterial pressure (119+/-8 mm Hg) and renal sympathetic nerve activity
(13+/-6 bars per cycle) returned to control levels. Bradycardiac and
tachycardiac responses to changes in blood pressure were reduced to 88
% and 89%, respectively, in rats with acute sinoaortic denervation and
76% and 74%, respectively, in rats with chronic sinoaortic denervatio
n. The reflex control of renal sympathetic nerve activity after acute
and chronic sinoaortic denervation showed an impairment of sympathoinh
ibition (0.13+/-0.02 and 0.25+/-0.1 bars per cycle, respectively, vers
us 0.9+/-0.17 bars per cycle in controls). Sympathoexcitatory response
s also were impaired in rats with acute and chronic sinoaortic denerva
tion (0.08+/-0.03 and 0.37+/-0.1 bars per cycle, respectively, compare
d with 0.98+/-0.2 bars per cycle in controls). The variability of mean
arterial pressure expressed by standard deviation was higher in rats
with acute and chronic sinoaortic denervation (13+/-2 and 15+/-2 mm Hg
, respectively) than in controls (6+/-3 mm Hg). The variability coeffi
cient of renal sympathetic nerve activity was lower 6 hours (0.22+/-0.
07) but normal 20 days after sinoaortic denervation (0.88+/-0.24 versu
s 0.77+/-0.06 in controls). We conclude that (1) acute sinoaortic dene
rvation increases arterial pressure and renal sympathetic nerve activi
ty and reduces renal sympathetic variability, (2) blood pressure and r
enal sympathetic activity return to normal levels in rats after chroni
c sinoaortic denervation, and (3) increased variability and impairment
of the baroreflexes persisted in the chronic phase of sinoaortic dene
rvation.