[Reactions of the respiratory neurons of the rat to increasing hypercapnia]

Responses of 247 ventrolateral medullary respiratory neurons (ambigual complex) to progressive hypercapnia were studied in anesthetized rats. In both transitory and steady state of the hypercapnia, activity of these cells was augmented: the number of spikes elevated, interspike intervals decreased, mean and instantaneous firing rates increased. At external levels of the hypercapnia the number of spikes as well as the burst duration were augmented in expiratory neurons. Distribution of interspike intervals was not changed.