The positioning of the hyoid bone under control modulated by the parasympathetic nervous system.

以往的研究表明，舌骨(GH)肌由舌下神经(XII)和颈段神经的传出轴突支配。为了阐明生长激素肌的这种双重神经支配的生理意义，我们用电生理和免疫组织化学方法研究了大鼠生长激素肌的传出神经支配的性质。来自支配生长激素肌肉的XII神经分支(GH.BR)的记录显示，假想吞咽时的脉冲爆发是通过XII神经干进行的。相反，生长激素的紧张性放电。BR均经颈总动脉入路完成。在体外，烟碱型乙酰胆碱受体(NAChR)的拮抗剂甲氨基甲胺和M_1受体的拮抗剂吡仑西平可取消紧张性作用。分离的XII神经节段与血管活性肠肽、nAChR和M_1受体抗血清孵育，均可产生少量标记神经元。所有标记的神经元直径相似，位于XII神经内侧支和外侧支分叉处近端约1.5 mm处。我们的发现表明，大鼠的生长激素肌肉既受到躯体神经系统的支配，也受到副交感神经系统的支配。

Previous studies have indicated that the geniohyoid (GH) muscle is innervated by efferent axons in the hypoglossal (XII) nerve and the ansa cervicalis. To clarify the physiological significance of this dual innervation of the GH muscle, we examined the properties of the efferent innervation of the rat GH muscle using eleotrophysiologioal and immunohistochenical methods. Recordings from the branch of the XII nerve that innervates the GH muscle (GH.Br) showed that bursts of impulses during fictitious swallowing were conducted via the XII nerve trunk. In contrast, tonic discharges in the GH. Br were conducted via the ansa cervicalis. Tonic activity was abolished in vitro by mecamylamine, an antagonist of the nicotinic acetylcholine receptor (nAChR), and by pirenzepine, an antagonist of the muscarinic M1 receptor. Incubation of isolated XII nerve segments with antisera to vasoactive intestinal peptide, nAChR, and the muscarinic M1 receptor yielded a small number of labeled neurons with each antiserum. All of the labeled neurons had similar diameters and were located approximately 1.5 mm proximal to the bifurcation of the XII nerve into its medial and lateral branches. Our findings indicate that the GH muscle in the rat is innervated by both the somatic and the parasympathetic nervous systems.