Localization and functional role of interneurons in the brainstem involved in chewing and swallowing

在清醒和麻醉的动物以及人类受试者中进行了电生理学研究。在动物实验中，脑干中的中间神经元活动是用咬肌、二腹肌和颏舌肌的肌电图记录的。电刺激下牙槽神经和上喉神经，分别诱发下颌反射和吞咽反射，同时刺激皮质咀嚼区，诱发虚构咀嚼。记录中间神经元和/或肌肉活动，以研究它们如何受到外周/中枢刺激的调节。记录中间神经元的活动非常困难，因为它们对呼吸也非常敏感，而呼吸也受到刺激的调节。因此，我们将目光转向输出系统以了解该功能。在动物的长期实验中，评估了咀嚼和吞咽过程中下颌反射反应的变化。结果表明，不仅咀嚼时反射受到抑制，吞咽时反射也受到抑制，并且与咀嚼时相比，吞咽时的调节是温和的。结果表明，运动神经元的调节输入独立存在于咀嚼中枢和吞咽中枢。另一方面，在人类中，研究了颏舌肌肌电图活动的调节模式，颏舌肌是一种外在舌头肌肉，已知其在制造食物团并将其通过口咽输送到食道方面发挥着关键作用。舌头的前部和后部由外周输入以不同的方式调节。它可能有助于完成摄入。

An electrophysiological study was performed in awake and anesthetized animals as well as human subjects. In animal experiments, interneuron activities in the brainstem were recorded with EMGs of masseter, digastric and genioglossus muscles. Electrical stimulation was applied in the inferior alveolar and superior laryngeal nerves to evoke the jaw reflex and swallowing reflex, respectively, while the cortical masticatory area was also stimulated to evoke the fictive mastication. Interneuron and/or muscle activity was recorded to investigate how they were modulated by the peripheral/central stimulation. It was very difficult to record interneuron activity because they were very sensitive to the respiration which was also modulated by the stimulation. We, therefore, moved our eyes to the output system to understand the function. In chronic experiments of animals, changes in jaw reflex responses were evaluated during chewing and swallowing. The results showed that the reflexes were suppressed not only during chewing but also during swallowing, and the modulation during swallowing was moderate as compared to that during chewing. The results suggest that the modulatory inputs to motoneurons exist from the chewing center and swallowing center independently. On the other hand, in humans, modulatory pattern was investigated in the EMG activity of the genioglossus muscle which was one of the extrinsic tongue muscles and was known to critically function as making the food bolus and transporting it through the oropharynx to the esophagus. the anterior and posterior portions of tongue were modulated by the peripheral inputs in a different manner. It may contribute to completion of ingestion.