Daily exercise and gender influence postexercise cardiac autonomic
responses in hypertensive rats.
Chen, Yifan, Margaret P. Chandler, and Stephen E. Dicarlo.
Department of Physiology, Northeastern Ohio Universities, College
of Medicine, Rootstown, Ohio 44272
APStracts 3:0469H, 1996.
The influence of daily spontaneous running (DSR) and gender on
postexercise cardiac autonomic responses were examined in
spontaneously hypertensive rats (SHR). Rats were weaned at 4-5 weeks
of age and randomly assigned to a sedentary (7 males and 6 females)
or DSR (7 males and 8 females) group. After 8 weeks of DSR or
sedentary control, rats were chronically instrumented with arterial
and venous catheters. After 5 days of recovery, cardiac sympathetic
(ST) and parasympathetic tonus (PT) were determined (by the response
of heart rate to receptor antagonists) on alternate days under two
experimental conditions: no-exercise and postexercise. After a single
bout of dynamic treadmill exercise (12 m/min, 10% grade for 40
minutes) ST was reduced (P< 0.05) (male sedentary: no-exercise
45 +/- 4 versus postexercise 28 +/- 3 bpm; female sedentary: no
-exercise 69 +/- 10 versus postexercise 37 +/- 7 bpm). PT was also
altered after exercise (male sedentary: no-exercise -31 +/- 4 versus
postexercise -11 +/- 2 bpm; female sedentary: no-exercise -5 +/- 4
versus postexercise 7 +/- 4 bpm). After DSR ST was reduced (male
sedentary 45 +/- 4 versus DSR 22 +/- 3 bpm; female sedentary 69 +/-
10 versus DSR 36 +/- 4 bpm) (P<0.05). Finally, male rats had a
lower ST and higher PT than female rats. These results demonstrate
that: 1) ST was reduced after a single bout of dynamic exercise; 2)
ST was reduced after DSR; 3) the autonomic response to acute exercise
was attenuated after DSR; 4) there was a gender influence on the
cardiac autonomic function.
Received 9 May 1996; accepted in final form 20 September 1996.
APS Manuscript Number H418-6.
Article publication pending Am. J. Physiol. (Heart Circ. Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 31 December 1996