Laryngeal effects and respiration in the suckling opossum.

Electromyogram (EMG) activity of the posterior cricoarytenoid (PCA muscles were active, but was otherwise closed. Larynx closure may contribute to the end-inspiratory pauses often observed in the intact animal. During inhalation of an asphyxiant test gas in place of room air, PCA and diaphragm activity generally increased; and increases in anesthesia decreased the EMG activity of both muscles. Water on the larynx transiently abolished both PCA and diaphragm discharge; but EMG activity returned to the PCA muscles before the diaphragm. Further, reactivation of the diaphragm was not always accompanied by a synchronized burst of PCA activity. Therefore, it is possible under some conditions to dissociate the motor outputs from the PCA muscles and diaphragm in this immature mammal.