Circulation research
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Circulation research · Oct 1975
Influence of cardiopulmonary vagal afferent activity on carotid chemoreceptor and baroreceptor reflexes in the dog.
The goal of this study was to determine if physiological levels of cardiopulmonary vagal afferent activity modulate carotid chemoreceptor and baroreceptor reflexes. In anesthetized, ventilated dogs, the aortic nerves and the cervical sympathetic trunks were cut, and atropine was administered so that vagotomy would interrupt only cardiopulmonary afferent impulses. Reflex vascular responses were observed in perfused gracilis muscle and hindpaw. ⋯ The results indicate that interruption of cardiopulmonary afferents potentiates the vascular and ventilatory responses to activation of the carotid chemoreceptors and augments the gain of the carotid baroreceptor reflex at low carotid pressures. These findings suggest that physiological levels of cardiopulmonary vagal afferent impulses suppress carotid baroreceptor and chemoreceptor reflexes through an interaction in the central nervous system. The suppressive effect on the chemoreceptor reflex may be distinct from tonic restraint of the vasomotor center by vagal afferents, since it involves sympathetic vasodilator as well as vasoconstrictor responses and may occur without suppression of base-line adrenergic constrictor tone.