The functional properties of the nerve supplying to muscles around the hyoid bone by using electrophysiological and HRP techniques

点击翻译按钮获取中文摘要

The previous studies indicate that the geniohyoid (GH) muscle receives its nerve supply via both the hypoglossal nerve and ansa cervicalis. However, the physiologic significance and properties of this dual innervation of the GH muscle have not yet been clarified. We examined the functional properties and distribution of the efferent and afferent components of the nerve supply to the rat GH muscle by using electrophysiological and horseradish peroxidase conjugated with wheat germ agglutinin retrograde labeling techniques. The present study provides several new findings concerning the neurons supplying the GH muscle. It was found that the GH muscle motoneurons related to swallowing are localized in the ventrolateral part of the hypoglossal nucleus. The activities of these motoneurons are conducted via the hypoglossal nerve trunk ; Synaptic transmission exists in the descending course to the GH muscle from the motoneurons located in the vicinity to the central canal, extending from approximately 0.5 to 1.0 mm caudal to the obex. The postsynaptic neurons are present in the region of the bifurcation point into the medial and lateral branched of the hypoglossal nerve. Afferent components from the proprioceptors of the GH muscle travel over the distal portion of the hypoglossal nerve to the ansa cervicalis, and then reach the primary sensory neurons located in the C1 spinal ganglia. The present results provide evidence that the GH muscle plays a significant role in the postural arrangement of the hyoid bone under control dependent on the autonomic nervous and somatic sensory systems.