First Department of Oral and Maxillofacial Surgery, Graduate School of Dentistry, Osaka University, Suita, Osaka, Japan.
J Neurophysiol. 2011 Dec;106(6):3129-35. doi: 10.1152/jn.01108.2010. Epub 2011 Sep 21.
The orexins (orexin-A and orexin-B) are neuropeptides that are secreted from neurons in the lateral hypothalamus and that participate in the regulation of feeding behavior. It remains to be determined, however, how the orexins exert their effects on feeding behavior, including masticatory movements. To this end, we analyzed food intake behavior and masticatory muscle activity using video analysis and electromyography (EMG) recording methods. The results showed that the cumulative food intake over 4 h was larger in rats intraventricularly injected with either orexin-A or orexin-B than in saline-injected control rats. The latency to eating and the feeding time for a fixed amount of pellets were shortened by injections of orexins in a dose-dependent manner, with a more potent effect by orexin-A than orexin-B. The shorter feeding time corresponded to a decreased number of chewing cycles. EMG recordings from both the digastric and masseter muscles showed two distinct patterns of bursts corresponding to the gnawing and chewing phases. After the injection of orexin-A, the magnitude of the bursts became larger in both phases in the masseter muscle, the burst duration became longer in the chewing phase in the masseter muscle, and the interburst interval became shortened in the gnawing phase in both muscles. Consequently, the burst frequency in the chewing phase was increased in the digastric muscle and, conversely, reduced in the masseter muscle. These results suggest that the orexin-A-induced facilitatory feeding behavior is characterized by a dynamic jaw-opener activity that opens the mouth rapidly and a powerful jaw-closer activity for crushing the increased amount of food taken into the mouth. The possible involvement of orexin-A in binge eating disorder is discussed.
食欲素（食欲素-A 和食欲素-B）是一种神经肽，由下丘脑外侧神经元分泌，参与调节进食行为。然而，食欲素如何对进食行为（包括咀嚼运动）发挥作用仍有待确定。为此，我们使用视频分析和肌电图（EMG）记录方法分析了食物摄入行为和咀嚼肌活动。结果表明，脑室注射食欲素-A 或食欲素-B 的大鼠在 4 小时内的累积食物摄入量大于生理盐水注射对照大鼠。食欲素注射以剂量依赖性方式缩短了进食潜伏期和固定量颗粒的进食时间，食欲素-A 的作用比食欲素-B 更强。较短的进食时间对应于咀嚼周期数的减少。来自二腹肌和咬肌的 EMG 记录显示出与咀嚼和咀嚼阶段相对应的两个明显的爆发模式。注射食欲素-A 后，咬肌的两个阶段的爆发幅度都变大，咬肌的咀嚼阶段的爆发持续时间变长，两个肌肉的咀嚼阶段的爆发间隔缩短。因此，咀嚼阶段的爆发频率在二腹肌中增加，而在咬肌中则相反地减少。这些结果表明，食欲素-A 诱导的促进进食行为的特征是快速张开嘴的动态开口器活动和用于粉碎进入口中的增加量食物的强大的闭口器活动。讨论了食欲素-A 可能参与暴食障碍。
