Modulation of the masseteric monosynaptic reflex by stimulation of the vestibular nuclear complex in rats

The effect of stimulation of the vestibular nuclear complex (VN) on the masseteric monosynaptic reflex (MMR) was studied in anesthetized rats. The MMR was evoked by electrical stimulation of the mesencephalic trigeminal nucleus and was recorded, bilaterally, as the electromyographic responses of the masseter muscles. Conditioning electrical stimulation of the medial vestibular nucleus (MVN) facilitated the MMR bilaterally, as did microinjection of monosodium glutamate into the MVN. In contrast, conditioning electrical stimulation of the inferior vestibular nucleus (IVN) inhibited the MMR bilaterally. Microinjection of monosodium glutamate into the IVN also inhibited the MMR bilaterally. Conditioning electrical stimulation of the lateral and superior vestibular nuclei did not modulate the MMR. These results suggest that the MVN and the IVN are involved in modulation of the MMR and plays an important role in controlling jaw movements.