Bio-X Institutes, Shanghai Jiao Tong University, Shanghai, China.
Affiliated Hospital of Nantong University, Nantong, Jiangsu, China.
Sleep. 2017 Dec 1;40(12). doi: 10.1093/sleep/zsx166.
The correlated activation of pre- and postsynaptic neurons is essential for the NMDA receptor-mediated Ca2+ influx by removing Mg2+ from block site and NMDA receptors have been implicated in phase resetting of circadian clocks. So we assessed rest:activity rhythms in Mg2+ block defective animals.
Using Drosophila locomotor monitoring system, we checked circadian rest:activity rhythms of different mutants under constant darkness (DD) and light:dark (LD) conditions. We recorded NMDA receptor-mediated currents or Ca2+ increase in neurons using patch-clamp and Ca2+ imaging techniques.
We found that Mg2+ block defective mutant flies were completely arrhythmic under DD. To further understand the role of Mg2+ block in daily circadian rest:activity, we observed the mutant files under LD cycles, and we found severely reduced morning anticipation and advanced evening peak compared to control flies. We also used tissue-specific expression of Mg2+ block defective NMDA receptors and demonstrated pigment-dispersing factor receptor (PDFR)-expressing circadian neurons were implicated in mediating the circadian rest:activity deficits. Endogenous functional NMDA receptors are expressed in most Drosophila neurons, including in a subgroup of dorsal neurons (DN1s). Subsequently, we determined that the uncorrelated extra Ca2+ influx may act in part through Ca2+/Calmodulin (CaM)-stimulated PDE1c pathway leading to morning behavior phenotypes.
These results demonstrate that Mg2+ block of NMDA receptors at resting potential is essential for the daily circadian rest:activity rhythms and we propose that Mg2+ block functions to suppress CaM-stimulated PDE1c activation at resting potential, thus regulating Ca2+ and cyclic AMP oscillations in circadian and sleep circuits.
前突触和后突触神经元的关联激活对于 NMDA 受体介导的 Ca2+内流至关重要，这种内流通过将 Mg2+从阻断部位移除，NMDA 受体被认为参与了生物钟的相位重设。因此，我们评估了 Mg2+阻断缺陷动物的休息-活动节律。
我们使用果蝇运动监测系统，在持续黑暗（DD）和明暗（LD）条件下检查不同突变体的昼夜休息-活动节律。我们使用膜片钳和 Ca2+成像技术记录神经元中的 NMDA 受体介导的电流或 Ca2+增加。
我们发现，Mg2+阻断缺陷突变体果蝇在 DD 条件下完全无节律。为了进一步了解 Mg2+阻断在每日昼夜休息-活动中的作用，我们在 LD 周期下观察了突变体文件，发现与对照果蝇相比，早晨预期和傍晚峰值严重降低。我们还使用组织特异性表达 Mg2+阻断缺陷 NMDA 受体，并证明表达色素扩散因子受体（PDFR）的生物钟神经元参与介导昼夜休息-活动缺陷。内源性功能性 NMDA 受体在大多数果蝇神经元中表达，包括在一组背侧神经元（DN1s）中表达。随后，我们确定，非相关的额外 Ca2+内流可能部分通过 Ca2+/钙调蛋白（CaM）刺激的 PDE1c 途径起作用，导致早晨行为表型。
这些结果表明，NMDA 受体在静息电位下的 Mg2+阻断对于每日昼夜休息-活动节律至关重要，我们提出 Mg2+阻断的作用是抑制静息电位下的 CaM 刺激的 PDE1c 激活，从而调节生物钟和睡眠电路中的 Ca2+和环 AMP 振荡。
