Piet Richard, Fraissenon Antoine, Boehm Ulrich, Herbison Allan E
Centre for Neuroendocrinology and Department of Physiology, Otago School of Medical Sciences, University of Otago, 9054 Dunedin, New Zealand, and.
Department of Pharmacology and Toxicology, University of Saarland School of Medicine, D-66421 Homburg, Germany.
J Neurosci. 2015 Apr 29;35(17):6881-92. doi: 10.1523/JNEUROSCI.4587-14.2015.
The cellular mechanisms governing the impact of the central circadian clock on neuronal networks are incompletely understood. We examine here the influence of the suprachiasmatic nucleus output neuropeptide arginine-vasopressin (AVP) on the activity of preoptic area kisspeptin neurons. These cells integrate circadian and hormonal signals within the neuronal network that regulates fertility in females. Electrophysiological recordings in brain slices from kisspeptin-GFP mice showed that AVP dose-dependently increased the firing rate of most kisspeptin neurons. These actions were mediated directly at the kisspeptin neuron. Experiments in mice expressing the calcium indicator GCaMP3 in kisspeptin neurons enabled simultaneous monitoring of intracellular calcium concentrations ([Ca(2+)]i) in multiple cells and revealed that AVP increased [Ca(2+)]i in >80% of diestrous kisspeptin neurons via a mechanism involving voltage-gated calcium channels. We next examined whether AVP signaling in kisspeptin neurons was time and ovarian cycle dependent. AVP exerted the same effects on diestrous and proestrous days of the ovarian cycle, whether hours before [zeitgeber time 4 (ZT4)-ZT6] or just before (ZT10) the expected time of the proestrous preovulatory luteinizing hormone surge. Remarkably, however, AVP signaling was critically dependent on circulating ovarian steroids as AVP no longer excited preoptic kisspeptin neurons in ovariectomized mice, an effect that was fully restored by estradiol treatment. Together, these studies show that AVP exerts a potent and direct stimulatory influence upon the electrical activity and [Ca(2+)]i of most preoptic kisspeptin neurons. Unexpectedly, estrogen is found to permit circadian AVP signaling at preoptic kisspeptin neurons rather than dynamically modulate its activity throughout the estrous cycle.
目前，人们对中枢生物钟影响神经网络的细胞机制尚未完全了解。我们在此研究视交叉上核输出神经肽精氨酸加压素（AVP）对视前区促性腺激素释放激素神经元活性的影响。这些细胞在调节雌性生育能力的神经网络中整合昼夜节律和激素信号。对促性腺激素释放激素绿色荧光蛋白（kisspeptin-GFP）小鼠脑片进行电生理记录显示，AVP呈剂量依赖性增加大多数促性腺激素释放激素神经元的放电频率。这些作用直接在促性腺激素释放激素神经元上介导。在促性腺激素释放激素神经元中表达钙指示剂GCaMP3的小鼠实验能够同时监测多个细胞内的钙浓度（[Ca(2+)]i），并揭示AVP通过涉及电压门控钙通道的机制使超过80%处于动情间期的促性腺激素释放激素神经元的[Ca(2+)]i增加。接下来，我们研究促性腺激素释放激素神经元中的AVP信号是否依赖时间和卵巢周期。无论在预期的动情前期促黄体生成素激增前数小时（生物钟时间4 [ZT4]-ZT6）还是就在其前（ZT10），AVP在卵巢周期的动情间期和动情前期均发挥相同作用。然而，值得注意的是，AVP信号严重依赖循环中的卵巢类固醇，因为AVP不再刺激去卵巢小鼠的视前区促性腺激素释放激素神经元，而雌二醇治疗可完全恢复这一效应。总之，这些研究表明AVP对大多数视前区促性腺激素释放激素神经元的电活动和[Ca(2+)]i具有强大而直接的刺激作用。出乎意料的是，发现雌激素允许视前区促性腺激素释放激素神经元存在昼夜节律性AVP信号，而不是在整个发情周期动态调节其活性。
