Arterial chemoreceptor influences on the laryngeal chemoreflex

Prolonged apnea and cardiovascular changes have been elicited in infant animals by the application of water to the laryngeal mucosa. Previous reports have produced conflicting evidence in regard to the possible role of arterial chemoreceptors in modulating this reflex. The present study was designed to determine the effect of carotid body stimulation or suppression on the duration of apnea and severity of cardiovascular changes in response to water in the larynx of piglets. The role of swallowing in terminating the apnea was also investigated. Hypoxia and isoproterenol, both carotid body stimuli, caused decreased apnea duration. Hyperoxia was associated with prolonged apnea duration; however, dopamine, which inhibits carotid body chemoreceptors, produced no significant change. Hypotension and bradycardia were only observed after prolonged apnea or chemoreceptor stimulation, supporting the concept that the cardiovascular component of the laryngeal chemoreflex is a result of changes in blood gas concentration rather than a direct response to laryngeal chemostimulation. The interval between water application and initiation of swallowing was not significantly affected by hypoxia or carotid body stimulation and swallowing did not always occur before resumption of breathing.