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

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 (PCA(I)) and D activities. Expiratory PCA (PCA(E)) was present but TA activity was absent. It was found that successive DECER, CBELL and PRG lesions attenuated PCA(E), 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 PCA(I) and D responses resembled apneusis and the E-load PCA(E) and D responses resembled central apnea.

CONCLUSION

The decreasing PCA(E) 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.