Department of Physiology and Pharmacology, College of Medicine, Chang Gung University, Tao-Yuan, 33305, Taiwan.
Healthy Aging Research Center, Chang Gung University, Tao-Yuan, 33305, Taiwan.
Sci Rep. 2017 Apr 4;7(1):640. doi: 10.1038/s41598-017-00699-3.
The suprachiasmatic nucleus (SCN) central clock comprises two coupled oscillators, with light entraining the retinorecipient vasoactive intestinal peptide (VIP)-positive ventrolateral oscillator, which then entrains the arginine vasopressin (AVP)-positive dorsomedial oscillator. While glucose availability is known to alter photic entrainment, it is unclear how the SCN neurones respond to metabolic regulation and whether the two oscillators respond differently. Here we show that the ATP-sensitive K (K) channel mediates differential responses to glucose shortage of the two oscillators. RT-PCR and electrophysiological results suggested the presence of Kir6.2/SUR1 K channels in the SCN neurones. Immunostaining revealed preferential distribution of Kir6.2 in the dorsomedial subregion and selective colocalization with AVP. Whole cell recordings with ATP-free pipette solution indicated larger tolbutamide-induced depolarisation and tolbutamide-sensitive conductance in dorsal SCN (dSCN) than ventral SCN (vSCN) neurones. Tolbutamide-sensitive conductance was low under perforated patch conditions but markedly enhanced by cyanide inhibition of mitochondrial respiration. Glucoprivation produced a larger steady-state inhibition in dSCN than vSCN neurones, and importantly hypoglycemia via opening K channels selectively inhibited the K-expressing neurones. Our results suggest that the AVP-SCN oscillator may act as a glucose sensor to respond to glucose shortage while sparing the VIP-SCN oscillator to remain in synch with external light-dark cycle.
视交叉上核（SCN）中央时钟由两个耦合振荡器组成，光使视网膜 VIP 阳性腹外侧振荡器同步，然后使精氨酸加压素（AVP）阳性背内侧振荡器同步。虽然已知葡萄糖的可用性会改变光同步，但尚不清楚 SCN 神经元如何对代谢调节做出反应，以及两个振荡器是否会做出不同的反应。在这里，我们表明，ATP 敏感的 K（K）通道介导了两个振荡器对葡萄糖缺乏的不同反应。RT-PCR 和电生理结果表明 SCN 神经元中存在 Kir6.2/SUR1 K 通道。免疫染色显示 Kir6.2 在背内侧亚区中优先分布，并与 AVP 选择性共定位。用无 ATP 的细胞内液记录表明，在背侧 SCN（dSCN）神经元中，托吡酯诱导的去极化和托吡酯敏感的电导率比腹侧 SCN（vSCN）神经元更大。在穿孔贴片条件下，托吡酯敏感的电导率较低，但被氰化物抑制线粒体呼吸显著增强。葡萄糖剥夺在 dSCN 神经元中产生比 vSCN 神经元更大的稳态抑制，重要的是，通过打开 K 通道，低血糖选择性抑制表达 K 的神经元。我们的结果表明，AVP-SCN 振荡器可能作为葡萄糖传感器，对葡萄糖缺乏做出反应，同时使 VIP-SCN 振荡器保持与外部光-暗周期同步。
