Abstract
For this article, the author investigated the synaptic relation ship between hypoglossal motor neurons and the surrounding interneurons in rats in the sucking stage. A series of three studies involving, retrograde study of hypoglossal nerve innervating on the tongue muscle, nystatin perforated whole-cell patch clamp investigation on the hypoglossal motor neuron and the morphology of hypoglossal motor neurons with biocytin, were designed to test this thesis. Retrograde study of hypoglossal neurons indicated that the hypoglossal nucleus was observed as on oval shaped region in the dorso-medial part of the brainstem. Whole cell patch clamp investigation of the hypoglossal motor neurons showed that stimulation of the surrounding areas evoked both excitatory and inhibitory postsynaptic potentials in the hypoglossal motor neurons. Most of these interneurons showed monosynaptic potential, and were intermingled in the surrounding area. Electrical stimulation of IOK, NX, PMn and LRt evoked a polysynaptic potential in the hypoglossal motor neurons. Biphasic postsynaptic potentials were elicited through electrical stimulation of GeV. Morphological study of the hypoglossal motor neuron indicated that hypoglossal motor neurons projecting into the surrounding interneurons were bipolar cells or pseudo-unipolar cells. The author concluded that interneurons of the area surrounding the hypoglossal nucleus may participate in the brainstem circuitry responsible for generating rhythmic tongue movements, and coordinate tongue movements with jaw movements.
