AJP - Heart and Circulatory Physiology, Vol 241, Issue 6 802-H806, Copyright © 1981 by American Physiological Society
Rapid resetting of the carotid baroreceptor reflex in the cat
D. L. Kunze
The carotid baroreceptor depressor reflex of the chloralose-anesthetized
cat was examined to determine the role of the prevailing carotid pressure
in determining the threshold, gain, and range of operation of the reflex
response. After the pressure of an isolated perfused carotid sinus was held
at 80 mmHg for 20 min the threshold pressure necessary to elicit the reflex
systemic blood pressure response was 78 +/- 2.9 (SE) mmHg (n = 5). When
carotid pressure was maintained for 20 min at 120 and 160 mmHg the
threshold rose to 113 +/- 2.9 and 126 +/- 3.0 mmHg, respectively. The
resetting of the threshold to a stable value upon elevating or reducing
carotid sinus pressure was accomplished within 15--20 min. The entire range
of operation of the reflex response was shifted to higher carotid pressures
as the holding pressure was elevated. The midrange gain of the response was
unchanged at the three holding pressures tested. These findings indicate
that the carotid baroreceptor reflex need not operate over a fixed range
but that the range may be rapidly adjustable to the prevailing pressure.
When arterial pressure is sustained at a level that is elevated or
depressed from normal the carotid baroreceptor reflex acutely resets to
operate in the range of the prevailing pressure with a threshold that has
moved toward the prevailing pressure.
