Lecturer, Assistant professor Department of Otolarynogology-Head and Neck Surgery Kyoto Prefectural University of Medicine Kyoto, Kyoto, Japan
Objective: The pontine respiratory group neurons in the dorsolateral pons contribute to the generation of respiratory rhythm, in particular, post inspiratory activity by regulating the glottic adduction during the early phase of expiration. In addition, these neurons could also mediate the likelihood of swallowing. However, little is known about the pontomedullary processing for swallowing motor pattern generation. The swallowing interneurons in the dorsal medulla are kernels for the swallowing center and play an essential role in swallowing pattern generation. Thus, we assess the effects of inhibition of the dorsolateral pons on the activities of swallowing interneurons as well as swallowing-related motor nerves during swallowing.
Method: Experiments were conducted using in situ arterially perfused brainstem preparation of decerebrate paralyzed rats. The hypoglossal, vagus, and phrenic nerves were recorded to identify fictive swallowing elicited by electrical stimulation of the superior laryngeal nerve and oral infusion of water. The activities of the swallowing interneurons were extracellularly recorded before and after inhibition of the ipsilateral dorsolateral pons using microinjection of GABA agonist. Results: Sequential pharyngeal swallowing could be induced by oral water injection after GABAergic inhibition of the dorsolateral pons. However, the motor nerve activities and swallowing latencies were typically decreased during electrically induced swallowing.
Conclusion: These findings suggest that the dorsolateral pons could contribute not only to the likelihood of swallowing but also to swallowing pattern generation and provide a view that pontomedullary neuronal networks are indispensable for swallowing motor processing.