The Electrical Activity of the Cricothyroid Muscles of the Cat

Abstract

AbstractIn the lightly anaesthetized preparations, the electrical activity of the cricothyroid ((IT) muscle of the cat was mainly of the expiratory type (figs. 1A, 6 and 8). Upon increasing the anaesthesia depth, expiratory activity was depressed or abolished and inspiratory discharges appeared, especially after increasing the respiratory dead space, after the occlusion of the tracheal cannula (fig. 1), or after inhalation of 8-10 % CO2 in oxygen. Discrete mechanical stimulation of the nasal and laryngeal mucosa and noxious stimuli applied to the skin of the face induced expiratory burst discharges in these conditions (fig. 2).Single unit analysis showed that the discharge patterns of the CT muscle may vary from the purely inspiratory type to the purely expiratory one, with all possible; intermediate combinations (fig. 3). Asphyxia and hypercapnia increased the number of inspiratory CT units (figs. 1 and 4). Expiratory activity was also augmented after strong asphyxia. Lung inflation generally decreased i...