Central orexin-A inhibits reflex swallowing via caudal brainstem

我们研究了食欲素对麻醉大鼠反射性吞咽的影响。将食欲素注入第四脑室。通过重复电刺激上级喉神经（SLN）的中央切断端诱导吞咽，并通过双极电极穿过下颌舌骨肌的肌电图导线识别吞咽。在SLN的电刺激过程中吞咽的频率下降后，食欲素-A的管理剂量依赖性的方式。给予orexin-A后，首次吞咽潜伏期有延长的趋势。食欲素-B的管理没有影响吞咽频率。预先给予orexin 1受体拮抗剂SB 334867，减弱了由orexin-A给药引起的吞咽频率抑制程度。为了鉴定食欲素-A的有效部位，评价了将食欲素-A微量注射到背侧迷走神经复合体（DVC）中的效果。将食欲素-A注射到外侧DVC、中间DVC或内侧DVC中的一个中。将orexin-A微量注射到DVC内侧，而不是其他两个部位，降低了吞咽频率。将SB 334867预注射到内侧DVC中破坏了由第四脑室给药orexin-A诱导的抑制反应。电毁损NTS连合部，但不消融AP，取消了由第四脑室给药orexin-A引起的吞咽反射抑制。这些结果表明，食欲素-A抑制反射吞咽通过食欲素1受体位于连合部分的NTS和/或其附近。

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.