Journal of Applied Physiology, Vol 62, Issue 6 2258-2263, Copyright © 1987 by American Physiological Society
Inhibition of aortic chemoreceptor discharge by pressor response to muscular contraction
K. W. McCoy, D. M. Rotto and M. P. Kaufman
We have examined the effect of static contraction of the hindlimb muscles
on the discharge of aortic chemoreceptors in chloralose-anesthetized cats.
The responses of the chemoreceptors to contraction were dependent on the
arterial pressure response to this maneuver. When contraction reflexly
evoked a pressor response of at least 20 mmHg, the discharge of 26
chemoreceptors was reduced from control levels by 53% (P less than 0.01).
The contraction-induced inhibition of chemoreceptor discharge was prevented
by phentolamine, an alpha-adrenergic antagonist that also attenuated the
contraction-induced pressor response. In addition, the inhibition evoked by
contraction was simulated by injection of phenylephrine and inflation of an
aortic balloon, both of which evoked pressor responses. However, when
contraction failed to significantly change arterial pressure, the discharge
of 20 aortic chemoreceptors was not significantly changed from control
levels. We conclude that the reflex pressor response to static contraction
inhibits the discharge of aortic chemoreceptors. This inhibition of
discharge needs to be considered when interpreting the effects of aortic
barodenervation on the cardiovascular responses to exercise.
