Carotid Bodies and Expiratory Muscle Recruitment

Abstract

e have reported previously (FASEB J 1989; 3:A401) that specific carotid body stimulation/inhibition tended to recruit/derecruit expiratory muscles in the same direction, and with similar time course, as the diaphragm in unanesthetized dogs (N = 5). One limitation of that study was the presence of pulmonary vagal afferent traffic that could have had an effect on expiratory muscle recruitment independent of the direct carotid body effects. To address this question, we blocked the pulmonary stretch receptor afferent traffic by bilateral cooling ofexteriorized (skin loops) cervical vagi in 3 awake, tracheotomized dogs. Excitatory (NaCN, 3-5 breaths N2) and inhibitory (dopamine, 3-5 breaths O ) stimuli of the carotid bodies during vagal blockade produced effects similar to those seen in nonblocked dogs; recruitment/derecruitment ofexpiratory musdes (triarigularis sterni, transversus abdominis) was in the same direction and had the same time course as changes in the crural diaphragm. We conclude that pulmonary stretch receptor afferents are not required for inspiratory or expiratory muscle recruitment/derecruitment in response to carotid body stimuli.