Laryngeal and diaphragmatic muscle activities after central nervous system lesions in cats

Abstract

Aim: To examine the central control and coordination of respiratory pump muscles and laryngeal valve muscles by systematic decerebration (DECER), cerebellectomy (CBELL), pontine respiratory group lesioning (PRG) and pontomedullary section (PMED). Methods: Activities of posterior cricoarytenoid (PCA), thyroarytenoid (TA) and diaphragm (D) muscles and their responses to inspiratory (I) and expiratory (E) total occlusions were determined in 10 adult cats. Results: INTACT anesthetized cats (n= 6) exhibited inspiratory PCA (PCAI) and D activities. Expiratory PCA (PCAE) was present but TA activity was absent. It was found that successive DECER, CBELL and PRG lesions attenuated PCAE, the intact pattern being noted in 7/10, 4/10 and 0/6 cats, respectively. After PMED, variable PCA, TA and continuous D activities occurred only with blood gas abnormalities. Augmented PCA and D responses to I- and E-loads occurred after PRG lesions: the I-load PCAI and D responses resembled apneusis and the E-load PCAE and D responses resembled central apnea. Conclusion: The decreasing PCAE activity observed with successive DECER, CBELL and PRG lesions suggests that these areas influence laryngeal abductor control of glottic size. The synchronous activities after PMED transection suggest a role for more rostral structures in coordinating laryngeal and diaphragmatic muscle activities.