Most inspiratory neurons in the pre-Bötzinger complex are suppressed during vomiting in dogs

Pulmonary ventilation is almost completely suppressed during actual retching. Correspondingly, respiratory activity either disappears or changes to retching activity in peripheral respiratory nerves and respiratory neurons of the Bötzinger complex and the caudal part of the ventral respiratory group. These results suggest the possibility that the respiratory rhythm generator is suppressed during retching. Recently, the pre-Bötzinger complex (pre-BOT) has been postulated to generate respiratory rhythm. To evaluate this possibility, the activities of pre-BOT neurons were observed during fictive retching and expulsion in decerebrate paralyzed dogs. Inspiratory (I) neurons in the pre-BOT consisted of pre-, early-, late-, post- and throughout-subtypes, as in cats and rats. Inspiratory firing almost completely disappeared during fictive retching in about 70% of the 158 pre-BOT I neurons examined, and changed to weak bursts produced either with retches or between retches in most of the remaining 30%. Similarly, all but one of the 21 I neurons examined did not produce any discharge with fictive expulsion. In contrast, all of the pre-BOT expiratory and inspiratory-expiratory neurons examined produced vigorous bursts either with retches or between retches, and with expulsion. These results suggest that inspiratory outputs from the respiratory rhythm generator are almost completely suppressed during retching and expulsion, and that expiratory outputs change to retching and expulsion activities.