Important role of carotid afferents in control of breathing

Abstract

The purpose of the present study was to determine the effect on breathing in the awake state of carotid body denervation (CBD) over 1-2 wk after denervation. Studies were completed on adult goats repeatedly before and 1) for 15 days after bilateral CBD (n = 8), 2) for 7 days after unilateral CBD (n = 5), and 3) for 15 days after sham CBD (n = 3). Absence of ventilatory stimulation when NaCN was injected directly into a common carotid artery confirmed CBD. There was a significant (P < 0.01) hypoventilation during the breathing of room air after unilateral and bilateral CBD. The maximum PaCO2 increase (8 Torr for unilateral and 11 Torr for bilateral) occurred approximately 4 days after CBD. This maximum was transient because by 7 (unilateral) to 15 (bilateral) days after CBD, PaCO2 was only 3-4 Torr above control. CO2 sensitivity was attenuated from control by 60% on day 4 after bilateral CBD and by 35% on day 4 after unilateral CBD. This attenuation was transient, because CO2 sensitivity returned to control temporally similar to the return of PaCO2 during the breathing of room air. During mild and moderate treadmill exercise 1-8 days after bilateral CBD, PaCO2 was unchanged from its elevated level at rest, but, 10-15 days after CBD, PaCO2 decreased slightly from rest during exercise. These data indicate that 1) carotid afferents are an important determinant of rest and exercise breathing and ventilatory CO2 sensitivity, and 2) apparent plasticity within the ventilatory control system eventually provides compensation for chronic loss of these afferents.

Changes in respiratory sensations induced by lobeline after human bilateral lung transplantation

“…Sensitivity of non-pulmonary receptors may have increased or plastic changes may have occurred in the CNS (e.g. Pan et al 1998). Changes secondary to altered pulmonary perfusion following angiogenesis may also be relevant.…”

Effect of N-acetyl-cysteine on the hypoxic ventilatory response and erythropoietin production: linkage between plasma thiol redox state and O2 chemosensitivity

“…1,2 This is exemplified by the O 2 -sensing arterial chemoreceptors that contribute significantly to regulation of the efferent respiratory drive and arterial PO 2 . 3,4 The hypoxic ventilatory response (HVR) is triggered by acute hypoxia and precedes a series of other hypoxic cellular responses that include changes in smooth muscle tone and the increased expression of hypoxia-inducible proteins such as erythropoietin (EPO). Earlier studies showed that the HVR decreases strongly with age 5,6 and is modulated by prolonged exposure to hypoxia 7 and by physical exercise.…”

Carotid body denervation alters ventilatory responses to ibotenic acid injections or focal acidosis in the medullary raphe

“…control of breathing; CO 2 chemoreception; peripheral chemoreception ONE ROLE OF THE PERIPHERAL chemoreceptors, or carotid bodies, relates to the ability to respond to changes in arterial O 2 and CO 2 , providing error feedback to the ventilatory control system (5, 13, 23). Additionally, the carotid bodies appear to provide a tonic excitatory input into the ventilatory control system, as evidenced by the effects of carotid body denervation (CBD) studies (7,12,19). CBD leads to hypoventilation during eupnea and exercise and to a reduction in CO 2 sensitivity.…”

“…Additionally, the carotid bodies appear to provide a tonic excitatory input into the ventilatory control system, as evidenced by the effects of carotid body denervation (CBD) studies (7,12,19). CBD leads to hypoventilation during eupnea and exercise and to a reduction in CO 2 sensitivity.…”