Interactions of the peripheral and central inputs on the swallowing initiation

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Swallowing is a primitive function necessary for the life support. Its motor behavior is controlled by a swallowing center, which is located in the medulla oblongata. This center generates highly coordinated motor sequence during swallowing. It is mainly composed of two parts; on e part consists of cells in the caudal region of the medulla and receives peripheral inputs; the other consists of motor nuclei in the ventral region of the medulla containing several cranial nerves, including the trigeminal (V), facial (VII), glossopharyngeal(IX), vagal(X) and hypoglossal(XII) nerves, operating the swallowing related muscies. It is also known that this mechanism receives inputs form other regions, such as respiratory center, chewing center and supramedullary regions. Interactions between the above mentioned regions are particularly unclear. The objective of the present study was to elucidate the interaction between these regions using freely behaving rabbits.It is concluded that advanced coordination may exist between the swallowing center, chewing center and supramedullary region. A hypothetic interaction between them is summarized.1)The swallowing center could not be under the fill control of the chewing center, but the generation of swallows might be controlled or synchronized by the chewing center.2) Conversely, the swallowing center might reset the chewing rhythm so that the chewing movement was slowed and the next chewing cycle began in the O_2 phase.3) The supramedullary region might send a tonic excitatory input to the swallowing center and maintain its excitability.4) The swallows elicited both by natural stlmull and the electrical SLN stimuli were concluded to be identical to each other.