Central orexin-A inhibits reflex swallowing via caudal brainstem

我们用麻醉大鼠研究了食欲素对反射性吞咽的影响。将促食欲素注入第四脑室。吞咽是通过反复电刺激喉上神经（SLN）中央切断端引起的，并通过双极电极穿过下颌舌骨肌的肌电图来识别。在给药后，电刺激SLN时吞咽频率呈剂量依赖性降低。食欲素- a给药后，首次吞咽潜伏期有延长的趋势。给药食欲素- b不影响吞咽频率。预给药食欲素1受体拮抗剂SB334867可减弱食欲素a对吞咽频率的抑制程度。为了确定orexin-A的有效部位，研究了在迷走背复合体（DVC）中微量注射orexin-A的效果。将Orexin-A注射到外侧DVC、中间DVC或内侧DVC。在内侧DVC微注射食欲素- a可降低吞咽频率，而其他两个部位没有。SB334867预注射内侧DVC破坏第四心室给药食欲素a诱导的抑制反应。NTS联合部分的电损伤，而非AP的消融，消除了第四心室给药食欲素a引起的反射性吞咽的抑制。这些结果表明，食欲素a通过位于NTS和/或其附近的食欲素1受体抑制反射性吞咽。

We examined the effects of orexins on the reflex swallowing using anaesthetized rats. Orexins were administered into the fourth ventricle. Swallowing was induced by repeated electrical stimulation of the central cut end of the superior laryngeal nerve (SLN) and was identified by the electromyogram lead penetrated the mylohyoide muscle through bipolar electrodes. The frequency of swallowing during the electrical stimulation of the SLN decreased after the administration of orexin-A in a dose-dependent manner. The latency of the first swallowing tended to be extended after the administration of orexin-A. The administration of orexin-B did not affect swallowing frequency. Pre-administration of SB334867, an orexin1 receptor antagonist, attenuated the degree of inhibition of swallowing frequency induced by the administration of orexin-A. To identify the effective site of orexin-A, the effect of a microinjection of orexin-A into the dorsal vagal complex (DVC) was evaluated. Orexin-A was injected into one of the lateral DVC, the intermediate DVC, or the medial DVC. Microinjection of orexin-A into the medial DVC but not the other two sites decreased swallowing frequency. Pre-injection of SB334867 into the medial DVC disrupted the inhibitory response induced by fourth ventricular administration of orexin-A. The electrical lesion of the commissural part of the NTS, but not ablation of the AP, abolished the inhibition of reflex swallowing induced by fourth ventricular administration of orexin-A. These results suggest that orexin-A inhibits reflex swallowing via orexin1 receptors situated in the commissural part of the NTS and/or its vicinity.