Neuronal gagging activity patterns may be generated by neurons in the reticular area dorsomedial to the retrofacial nucleus in dogs

Expulsion is induced when hypercapnea and hypoxia develop during retching, or when the oropharyngeal mucosa is irritated (the gag reflex). The central pattern generator (CPG) for expulsion has been suggested to coexist with the CPG for retching in the reticular area dorsomedial to the retrofacial nucleus, which may correspond to the Botzinger complex (BOT). However, its participation in gagging induced by oropharyngeal irritation is unclear. To elucidate such participation, the firing patterns of BOT neurons were observed during gagging induced by stimulation of superior laryngeal afferents in decerebrate, paralyzed dogs. Only 23% of inspiratory and 34% of expiratory BOT neurons increased their firing in response to stimulation of the superior laryngeal nerve. In contrast, 75% of nonrespiratory BOT neurons showed enhanced firing with this stimulation. During gagging, each nonrespiratory, inspiratory, and expiratory BOT neuron fired with the same pattern that they exhibited during expulsion caused by changes in blood gases. These firing patterns could be classified into five types and are thought to be appropriate for generating neuronal gagging activity. These results suggest that the CPG for expulsion in the BOT produces gagging when it is activated by oropharyngolaryngeal afferents.