Interactions between swallowing centre, chewing centre and supramedullary region during elicitation of swallows by superior laryngeal nerve (SLN) stimulation

Abstract

Swallowing centre (swl-c) which controls motor behaviour of swallowing receives inputs from other regions including respiratory center, chewing center (chw-c) and supramedullary region. However, interactions between them are unclear. The objective of this study was to elucidate such interactions using freely behaving six domestic male rabbits. Swallows were elicited by superior laryngeal nerve (SLN) stimulation. The electromyographic activities (EMGs) of masticatory and swallowing muscles and the jaw movement orbits were recorded for 30 s with and without SLN stimulation at rest and during chewing. Decerebration was performed to investigate the influence of supramedullary region. Although there was a significant increase (P < 0·001) in the number of swallows between with and without SLN stimulation at rest and during chewing, the absolute increase in the number of swallows was same. After decerebration, the number of swallows was decreased significantly (P < 0·05). There were no significant differences in the latency of thyrohyoid EMG onset and cycle durations between with and without SLN stimulation. It is concluded that (i) swallows induced by SLN stimulation may be identical to those induced by food bolus, (ii) generation of swallows by swl-c might be controlled by chw-c, (iii) swl-c might affect the rhythm generator in chw-c and (iv) supramedullary region might send a tonic excitatory input to swl-c and maintains its excitability. Supported by Japan grants – in-aid #1470389 and #12771102.