Effect of peripherally and cortically evoked swallows on jaw reflex responses in anesthetized rabbits

• Published in: Brain research 2018-09, Vol.1694, p.19-28
• Main Authors: Suzuki, Taku, Yoshihara, Midori, Sakai, Shogo, Tsuji, Kojun, Nagoya, Kouta, Magara, Jin, Tsujimura, Takanori, Inoue, Makoto
• Format: Article
• Language: English
• Subjects: Cortical swallowing area; Jaw-closing reflex; Jaw-opening reflex; Rabbit; Superior laryngeal nerve; Swallow
• ISSN: 0006-8993; 1872-6240
• DOI: 10.1016/j.brainres.2018.05.002

•Jaw-opening reflex reduces during peripherally and centrally evoked swallowing.•Reduction rate depends on the current intensity of conditioning stimulation.•The reduction is larger during central stimulation than peripheral stimulation.•Jaw-closing reflex responses are not affected during swallowing. This study aimed to investigate whether the jaw-opening (JOR) and jaw-closing reflexes (JCR) are modulated during not only peripherally, but also centrally, evoked swallowing. Experiments were carried out on 24 adult male Japanese white rabbits. JORs were evoked by trigeminal stimulation at 1 Hz for 30 s. In the middle 10 s, either the superior laryngeal nerve (SLN) or cortical swallowing area (Cx) was simultaneously stimulated to evoke swallowing. The peak-to-peak JOR amplitude was reduced during the middle and late 10-s periods (i.e., during and after SLN or Cx stimulation), and the reduction was dependent on the current intensity of SLN/Cx stimulation: greater SLN/Cx stimulus current resulted in greater JOR inhibition. The reduction rate was significantly greater during Cx stimulation than during SLN stimulation. The amplitude returned to baseline 2 min after 10-s SLN/Cx stimulation. The effect of co-stimulation of SLN and Cx was significantly greater than that of SLN stimulation alone. There were no significant differences in any parameters of the JCR between conditions. These results clearly showed that JOR responses were significantly suppressed, not only during peripherally evoked swallowing but also during centrally evoked swallowing, and that the inhibitory effect is likely to be larger during centrally compared with peripherally evoked swallowing. The functional implications of these results are discussed.