Effects of the inferior alveolar nerve stimulation on tongue muscle activity during mastication in freely behaving rabbits.

Genioglossus (Gg) reflexes elicited by electrical stimulation of the inferior alveolar nerve were examined in naturally chewing rabbits. To eliminate possible contaminations of the digastric (Dig) activity in the Gg responses, the Dig nerve was denervated bilaterally. Masticatory and tongue muscles were well coordinated during chewing after the denervation; i.e., there were no significant differences in the phase durations between before and after denervation. The Gg reflex measured was divided into three categories depending on the chewing phase (i.e., jaw-opening, OP; fast-closing, FC; and slow-closing, SC) in which the stimulus was delivered. The reflex amplitude was phasically modulated for the phases, in that the amplitude in the OP phase was larger than that in any other phase (P<0.05). On the other hand, the amplitude in the FC and SC phases was not significantly different to each other and from the control value obtained when the animal was awake and resting. The pattern of the modulation in the reflex amplitude was different from the previous report as to the Dig reflex in that OP