Electrophysiological analysis of the lateral reticular formation controlling orofacial autonomic and motor functions

通过解剖学、电生理学和行为学研究，研究了神经网络在脑干辅助自主神经和运动口腔功能中的作用。在解剖学研究中，将FTTC和罗丹明分别注入大鼠舌前部或颌下腺的分泌神经，观察到支配舌和颌下腺的上唾液神经元。两组SS神经元形态相似，混杂在外侧网状结构中。在电生理研究中，采用全细胞膜片钳技术分析脑干切片中SS神经元的生物物理特性。支配舌的SS神经元表现出显著的瞬时外向电流(A-电流)，放电频率高达70赫兹。那些支配唾液腺的人表现出持续时间更长的电流，并发射高达30赫兹的电流。比较1周龄和2周龄大鼠的A电流，观察A电流在出生后的发育。在行为学研究中，从自由活动的大鼠颌下腺记录到唾液流量和咬肌活动，在咀嚼过程中，唾液量和肌肉活动并不总是平行的，这可能对自主神经和运动功能有不同的离心力作用。通过这些研究，我们得出结论，自主神经和运动口腔功能受到高级中枢神经系统的控制，但在下脑干，特别是外侧网状结构中，两者之间存在一个接触点。还需要进一步的研究来澄清进食行为和舌头血流速度之间的关系。

Neural network in the brainstem subserving autonomic and motor oral functions was investigated by anatomical, electrophysiological and behavioral studies. In the anatomical study, FTTC and Rhodamine were injected into the anterior part of the tongue or the secretory nerve of the subamndibular gland, respectively, and the superior salivatory (SS) neurons innervating the tongue and those innervating the submandibular salivary glands were identified in rats. The two groups of SS neurons were similar in shape and intermingled in the lateral reticular formation. In the electrophysiological study, biophysical properties of the SS neurons were analyzed by the whole-cell patch clamp technique in sliced brainstem preparations. The SS neurons innervating the tongue displayed a prominent transient outward current (A-current), and fired up to 70 Hz. Those innervating the salivary glands expressed A current lasting longer period, and fired up to 30 Hz. Post-natal development of the A-currents was observed when we compared between A- currents of one-week and two-week old rats. In behavioral study, salivary flow from the submandibular gland and activity of the masseter muscle were chronically recorded from the freely moving rats, During chewing, the amount of saliva and muscle activity were not always parallel, suggesting different centrifugal effects on autonomic and motor functions.Through these studies, we conclude that the autonomic and motor oral functions are under control from the higher central nervous system, but there is a contact point between the two functions in the lower brainstem especially the lateral reticular formation. A further study is needed to clarify relationship between feeding behavior and blood flow rate of the tongue.