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

以往的研究表明，颧舌骨肌(GH)通过舌下神经和颈段接受神经供应。然而，生长激素肌的这种双重神经支配的生理意义和性质尚未阐明。我们用电生理和辣根过氧化物酶标记麦芽凝集素逆行标记技术，研究了大鼠生长激素肌肉神经供应的传出和传入成分的功能特性和分布。本研究提供了几个有关供应生长激素肌肉的神经元的新发现。结果发现，与吞咽有关的生长激素肌运动神经元定位于舌下核腹外侧部。这些运动神经元的活动通过舌下神经干进行，从位于中央管附近的运动神经元向生长激素肌的下行过程中存在突触传递，从尾侧约0.5~1.0 mm延伸到OBEX。突触后神经元位于舌下神经内侧支和外侧支的分叉点区域。来自生长激素肌肉本体感受器的传入成分穿过舌下神经的远端到达颈段，然后到达位于颈1脊神经节的初级感觉神经元。这些结果证明生长激素肌肉在舌骨的体位排列中起着重要的作用，它依赖于自主神经和躯体感觉系统的控制。

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.