The importance of neurons in the solitary tract nucleus (NTS) in the production of coughing was tested by microinjections of the non-specific glutamate receptor antagonist kynurenic acid (kyn; 100 mM in artificial cerebrospinal fluid) in 15 adult spontaneously breathing anesthetized cats. Repetitive coughing was elicited by mechanical stimulation of the intrathoracic airway. Electromyograms (EMG) were recorded from inspiratory parasternal and expiratory transversus abdominis muscles (ABD). Bilateral microinjections of kyn into the NTS rostral to obex (55±4 nl total in two locations; n=6 or 110±4 nl total in four locations; n=5), primarily the ventrolateral subnucleus, reduced cough number and expiratory cough efforts (amplitudes of ABD EMG and maxima of esophageal pressure) compared to control. These microinjections also markedly prolonged the inspiratory phase, all cough related EMG activation, and the total cough cycle duration as well as some other cough related time intervals. In response to microinjections of kyn into the NTS rostral to the obex respiratory rate decreased, and there were increases in the durations of the inspiratory and post-inspiratory phases and mean blood pressure. However, bilateral microinjections of kyn into the NTS caudal to obex as well as control vehicle microinjections in the NTS location rostral to obex had no effect on coughing or cardiorespiratory variables. These results are consistent with the existence of a critical component of the cough rhythmogenic circuit located in the rostral ventral and lateral NTS. Neuronal structures of the rostral NTS are significantly involved specifically in the regulation of the cough magnitude and phase timing.
- cough phase timing
- Copyright © 2016, Journal of Neurophysiology