Orexin/hypocretin has been implicated in central motor control. The gigantocellular reticular nucleus (Gi), a key element of the brainstem motor inhibitory system, also receives orexinergic innervations. However, the modulations of orexin on the neuronal activities and the underlying cellular mechanisms in Gi neurons remain unknown. Here, through whole-cell patch-clamp recordings, we first observed that orexin increased the firing frequency in Gi neurons. Interestingly, a postsynaptic depolarization elicited by orexin was observed in the presence of tetrodotoxin, without altering the input resistance of Gi neurons at around −60 mV. Moreover, through comparing the current-frequency curves constructed by identical current injections from equal membrane potentials, we found that orexin also increased the repetitive firing ability of Gi neurons. This action appeared to be caused by the shortening of inter-spike intervals, without altering the waveform of individual action potentials. We finally revealed that activation of the non-selective cationic conductance contributed to the orexin-elicited excitation in Gi neurons. Together, these results suggest that orexin may facilitate Gi-mediated motor functions through enhancing the neuronal activities of Gi neurons.

Orexin / hypocretin与中央运动控制有关。大脑干网状细胞核（Gi），脑干运动抑制系统的关键要素，也接受奥瑞西能神经支配。然而，食欲素对Gi神经元神经元活动和潜在的细胞机制的调节仍然未知。在这里，通过全细胞膜片钳记录，我们首先观察到orexin增加了Gi神经元的放电频率。有趣的是，在存在河豚毒素的情况下，观察到了由orexin引起的突触后去极化，而在-60 mV附近未改变Gi神经元的输入电阻。此外，通过比较由相同的膜电位从相同的电流注入构建的电流-频率曲线，我们发现食欲肽还增加了Gi神经元的重复放电能力。该动作似乎是由于尖峰间隔的缩短而引起的，而没有改变单个动作电位的波形。我们最终揭示了非选择性阳离子电导的激活促成了Gi在神经元中由orexin引起的兴奋。总之，这些结果表明，orexin可能通过增强Gi神经元的神经元活性来促进Gi介导的运动功能。