Peripheral chemoreceptors determine the respiratory sensitivity of central chemoreceptors to CO₂

Abstract

We assessed the contribution of carotid body chemoreceptors to the ventilatory response to specific CNS hypercapnia in eight unanaesthetized, awake dogs. We denervated one carotid body (CB) and used extracorporeal blood perfusion of the reversibly isolated remaining CB to maintain normal CB blood gases (normoxic, normocapnic perfusate), to inhibit (hyperoxic, hypocapnic perfusate) or to stimulate (hypoxic, normocapnic perfusate) the CB chemoreflex, while the systemic circulation, and therefore the CNS and central chemoreceptors, were exposed consecutively to four progressive levels of systemic arterial hypercapnia via increased fractional inspired CO 2 for 7 min at each level. Neither unilateral CB denervation nor CB perfusion, per se, affected breathing. Relative to CB control conditions (normoxic, normocapnic perfusion), we found that CB chemoreflex inhibition decreased the slope of the ventilatory response to CNS hypercapnia in all dogs to an average of 19% of control values (range 0-38%; n = 6), whereas CB chemoreflex stimulation increased the slope of the ventilatory response to CNS hypercapnia in all dogs to an average of 223% of control values (range 204-235%; n = 4). We conclude that the gain of the CNS CO 2 /H + chemoreceptors in dogs is critically dependent on CB afferent activity and that CNS-CB interaction results in hyperadditive ventilatory responses to central hypercapnia.

Breathing without CO2Chemosensitivity in ConditionalPhox2bMutants

“…The latter result suggested already that the mutants rely more on input from the CBs than the controls do. This interpretation was amply confirmed when we tested their response to pure O 2 , known to inhibit peripheral chemoreceptor input (a manipulation called physiological chemodenervation) (Dejours, 1962;Hertzberg et al, 1990;Blain et al, 2010). Strikingly, this maneuver triggered periodic breathing-a series of deep breaths interrupted by prolonged apneas (Darnall, 2010)-in all mutants but not in controls.…”

“…A key tenet in respiratory physiology states that arterial PCO 2 is the essential drive to breathe, and sentences abound in the recent literature such as "CO 2 provides the major tonic drive to breathe" (Spyer and Gourine, 2009) or "we have known for more than a century that the levels of CO 2 in the systemic circulation and in the brain are the major determinants of breathing in humans and other mammals" (Blain et al, 2010). Here we have revisited this dogma using a new mouse mutant.…”

Neonatal stress and attenuation of the hypercapnic ventilatory response in adult male rats: the role of carotid chemoreceptors and baroreceptors

“…On the basis of indirect evidence indicating that NMS augments carotid body's responsiveness to hypoxia (35,36), it was proposed that the relative hyperoxia that occurs during hypercapnic hyperpnea [ϳ20 mmHg increase (34)] is sufficient to attenuate the CO 2 response of NMS rats (21). However, the recent evidence indicating that central and peripheral chemoreceptors are interdependent and influence each other's sensitivity (4,10,11,57) raises the possibility that NMS disrupts this interaction.…”

Hallazgo Incidental De Un Quimiodectoma en Un Canino Bulldog Inglés

“…Los cuerpos superiores lo que ocasionaría el incremento de la aórtico y carotídeo son órganos quimiorreceptores presión negativa durante la inspiración resultando en sensitivos a variaciones del pH sanguíneo, tensión de fenómenos secundarios como el colapso laríngeo. Las oxígeno y contenido de dióxido de carbono, de modo lesiones del tejido blando derivarían en una hipoxia que auxilian en la regularización de la respiración y la crónica que conduciría a una hiperplasia de los circulación (2,3,4). Basados en esta función, estos quimiorreceptores, pudiendo transformarse en una tumores fueron llamados también quimiodectomas.…”