Neuroscience Graduate Program, School of Medicine, Oregon Health & Science University, Portland, OR, 97239, USA.
Oregon Institute for Occupational Health Sciences, School of Medicine, Oregon Health & Science University, Portland, OR, 97239, USA.
Sci Rep. 2017 Aug 31;7(1):10226. doi: 10.1038/s41598-017-09778-x.
Several reports have described excitatory GABA transmission in the suprachiasmatic nucleus (SCN), the master pacemaker of circadian physiology. However, there is disagreement regarding the prevalence, timing, and neuronal location of excitatory GABA transmission in the SCN. Whether GABA is inhibitory or excitatory depends, in part, on the intracellular concentration of chloride ([Cl]). Here, using ratiometric Cl imaging, we have investigated intracellular chloride regulation in AVP and VIP-expressing SCN neurons and found evidence suggesting that [Cl] is higher during the day than during the night in both AVP+ and VIP+ neurons. We then investigated the contribution of the cation chloride cotransporters to setting [Cl] in these SCN neurons and found that the chloride uptake transporter NKCC1 contributes to [Cl] regulation in SCN neurons, but that the KCCs are the primary regulators of [Cl] in SCN neurons. Interestingly, we observed that [Cl] is differentially regulated between AVP+ and VIP+ neurons-a low concentration of the loop diuretic bumetanide had differential effects on AVP+ and VIP+ neurons, while blocking the KCCs with VU0240551 had a larger effect on VIP+ neurons compared to AVP+ neurons.
已有数份报告描述了视交叉上核（SCN）中的兴奋性 GABA 传递，SCN 是生理节律的主起搏器。然而，关于 SCN 中兴奋性 GABA 传递的普遍性、时间和神经元位置仍存在分歧。GABA 是否具有兴奋性取决于氯离子（[Cl]）的细胞内浓度。在这里，我们使用比率型 Cl 成像研究了 AVP 和 VIP 表达的 SCN 神经元中的细胞内氯离子调节，发现有证据表明，在 AVP+和 VIP+神经元中，[Cl]白天高于夜间。然后，我们研究了阳离子氯离子共转运体对这些 SCN 神经元中[Cl]的调节作用，发现氯离子摄取转运体 NKCC1 有助于 SCN 神经元中的[Cl]调节，但 KCCs 是 SCN 神经元中[Cl]的主要调节剂。有趣的是，我们观察到[Cl]在 AVP+和 VIP+神经元之间存在差异调节-低浓度的Loop 利尿剂布美他尼对 AVP+和 VIP+神经元具有不同的影响，而用 VU0240551 阻断 KCCs 对 VIP+神经元的影响比对 AVP+神经元的影响更大。
