Melatonin promotes sleep in mice by inhibiting orexin neurons in the perifornical lateral hypothalamus
Melatonin promotes sleep in mice by inhibiting orexin neurons in the perifornical lateral hypothalamus
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DOI：
10.1111/jpi.12498
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发表时间：
2018-09-01
影响因子：
10.3
通讯作者：
Thakkar, Mahesh M.
中科院分区：
文献类型：
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作者：
Sharma, Rishi;Sahota, Pradeep;Thakkar, Mahesh M.
褪黑素促进睡眠。然而，其潜在机制尚不清楚。下丘脑穹窿周围外侧部（PFH）的食欲素神经元在唤醒促进中起关键作用。褪黑激素通过抑制食欲素神经元促进睡眠吗？我们使用C57 BL/6 J小鼠并设计了4个实验来解决这个问题。实验1使用双标记免疫荧光和检查食欲素神经元上的褪黑激素受体的存在。第二，小鼠，植入双侧导向器靶向PFH和睡眠记录电极，注入褪黑激素（500 pmole/50 nL/侧）在黑暗开始（活跃期的开始），和自发发作的睡眠觉醒进行了检查。第三，将双侧引导物植入PFH的小鼠在黑暗开始时注入褪黑激素（500 pmole/50 nL/侧），并在2 h后安乐死，以检测食欲素神经元中c-Fos表达的食欲素神经元的激活。第四，植入PFH双侧引导器和睡眠记录电极的小鼠在轻发作（睡眠期开始）时被注入褪黑激素受体拮抗剂Luzindole（10 pmol/50 nL/侧），并检查自发的睡眠-觉醒发作。我们的研究结果表明，食欲素神经元表达MT 1，但不MT 2受体。褪黑激素输注到PFH，在黑暗开始，位点特异性和显着增加NREM睡眠（43.7%，P = 0.003）和减少觉醒（12.3%，P = 0.013）。局部褪黑激素输注在黑暗中出现抑制食欲素神经元的明显减少（66%，P = 0.0004）的食欲素神经元表达c-Fos的数量。最后，luzindole输注诱导的在睡眠开始时阻断PFH中的褪黑激素受体显著增加觉醒（44.1%，P = .015）。基于这些结果，我们认为褪黑激素可能通过MT 1受体抑制食欲素神经元和促进睡眠。
Melatonin promotes sleep. However, the underlying mechanisms are unknown. Orexin neurons in the perifornical lateral hypothalamus (PFH) are pivotal for wake promotion. Does melatonin promote sleep by inhibiting orexin neurons? We used C57BL/6J mice and designed 4 experiments to address this question. Experiment 1 used double-labeled immunofluorescence and examined the presence of melatonin receptors on orexin neurons. Second, mice, implanted with bilateral guides targeted toward PFH and sleep-recording electrodes, were infused with melatonin (500pmole/50nL/side) at dark onset (onset of active period), and spontaneous bouts of sleep-wakefulness were examined. Third, mice, implanted with bilateral guides into the PFH, were infused with melatonin (500pmole/50nL/side) at dark onset and euthanized 2hours later, to examine the activation of orexin neurons using c-Fos expression in orexin neurons. Fourth, mice, implanted with PFH bilateral guides and sleep-recording electrodes, were infused with melatonin receptor antagonist, luzindole (10pmol/50nL/side), at light onset (onset of sleep period), and spontaneous bouts of sleep-wakefulness were examined. Our results suggest that orexin neurons express MT1, but not MT2 receptors. Melatonin infusion into the PFH, at dark onset, site-specifically and significantly increased NREM sleep (43.7%, P = .003) and reduced wakefulness (12.3%, P = .013). Local melatonin infusion at dark onset inhibited orexin neurons as evident by a significant reduction (66%, P = .0004) in the number of orexin neurons expressing c-Fos. Finally, luzindole infusion-induced blockade of melatonin receptors in PFH at sleep onset significantly increased wakefulness (44.1%, P = .015). Based on these results, we suggest that melatonin may act via the MT1 receptors to inhibit orexin neurons and promote sleep.