Important role of carotid chemoreceptor afferents in control of breathing of adult and neonatal mammals

This review provides a summary and prospective on the importance of carotid /peripheral chemoreceptors to the control of breathing during physiologic c onditions. For several days after carotid body denervation (CBD), adult mam mals hypoventilate (+ 10 mmHg increase in Pa-CO2) at rest and during exerci se and CO2 sensitivity is attenuated by about 60%. In addition, if the rost ral ventrolateral medulla is cooled during NREM sleep after CBD, a sustaine d apnea is observed. Eventually, days or weeks after CBD, a peripheral vent ilatory chemoreflex redevelops and there is a normalization of breathing (r est and exercise) and CO2 sensitivity. The site (s) of the regained chemose nsitivity has not been established. This plasticity/redundancy after CBD ap pears greater in neonates than in adult mammals. These data suggest the car otid and other peripheral chemoreceptors provide an important excitatory in put to medullary respiratory neurons that is essential for breathing when w akeful stimuli and central chemoreceptors are absent. (C) 2000 Elsevier Sci ence B.V. All rights reserved.