Reflex responses in the infrahyoid muscles by mechanical stimulation of the tongue in the frog.

Abstract

In order to investigate the reflex regulation of the infrahyoid muscle activities induced by sensory signals (chemical and mechanical) from the tongue in the frog, excitatory and inhibitory reflex responses in the infrahyoid muscles (sternohyoid muscle-SH muscle, omohyoid muscle-OH muscle) by both chemical and mechanical stimulation of the tongue were studied using electromyography (EMG) recordings in bullfrogs, Rana catesbeiana. The chemical stimulations (1 mM quinine-HCl, 0.5-1.5 M NaCl) evoked no reflex response in either the SH or the OH muscles, and this result suggested that the infrahyoid muscle activities may not be reflexly regulated by chemical signals from the tongue in the bullfrog. Both the mechanical stimulation of the tongue and the electrical stimulation of the glossopharyngeal nerve evoked excitatory responses in the SH and the OH muscles, bilaterally and contralaterally, respectively. The electrical stimulation of the glossopharyngeal nerve evoked no inhibitory response in the SH, while the stimulation evoked the inhibitory response in the ipsilateral OH. These differences may be related to a difference in the role of these muscles during tongue movement in the bullfrog.