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首页> 外文期刊>Proceedings of the National Academy of Sciences of the United States of America >Intrinsic, nondeterministic circadian rhythm generation in identified mammalian neurons
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Intrinsic, nondeterministic circadian rhythm generation in identified mammalian neurons

机译：确定的哺乳动物神经元内在的，不确定性的昼夜节律产生

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摘要

Circadian rhythms are modeled as reliable and self-sustained oscillations generated by single cells. The mammalian suprachiasmatic nucleus (SCN) keeps near 24-h time in vivo and in vitro, but the identity of the individual cellular pacemakers is unknown. We tested the hypothesis that circadian cycling is intrinsic to a unique class of SCN neurons by measuring firing rate or Period2 gene expression in single neurons. We found that fully isolated SCN neurons can sustain circadian cycling for at least 1 week. Plating SCN neurons at <100 cells/mm~2 eliminated synaptic inputs and revealed circadian neurons that contained arginine vasopressin (AVP) or vasoactive intestinal polypeptide (VIP) or neither. Surprisingly, arrhythmic neurons (nearly 80% of recorded neurons) also expressed these neuropeptides. Furthermore, neurons were observed to lose or gain circadian rhythmic-ity in these dispersed cell cultures, both spontaneously and in response to forskolin stimulation. In SCN explants treated with tetrodotoxin to block spike-dependent signaling, neurons gained or lost circadian cycling over many days. The rate of PERIOD2 protein accumulation on the previous cycle reliably predicted the spontaneous onset of arrhythmicity. We conclude that individual SCN neurons can generate circadian oscillations; however, there is no evidence for a specialized or anatomically localized class of cell-autonomous pacemakers. Instead, these results indicate that AVP, VIP, and other SCN neurons are intrinsic but unstable circadian oscillators that rely on network interactions to stabilize their otherwise noisy cycling.
机译：昼夜节律被建模为由单个细胞产生的可靠且自持的振荡。哺乳动物视交叉上核（SCN）在体内和体外保持近24小时的时间，但单个细胞起搏器的身份尚不清楚。我们通过测量单个神经元的放电频率或Period2基因表达，检验了昼夜节律是SCN神经元的独特类别固有的假设。我们发现完全隔离的SCN神经元可以维持昼夜节律周期至少1周。以低于100个细胞/ mm〜2的速度接种SCN神经元，消除了突触输入，并揭示了含有精氨酸加压素（AVP）或血管活性肠多肽（VIP）或两者都不含有的昼夜节律神经元。令人惊讶的是，心律不齐的神经元（几乎记录的神经元的80％）也表达了这些神经肽。此外，观察到神经元在这些分散的细胞培养物中自然地失去或获得昼夜节律性，这既是自发的又是对毛喉素刺激的响应。在用河豚毒素处理的SCN外植体中，阻断了依赖于刺突的信号传导，神经元在许多天内获得或失去了昼夜节律循环。前一个周期的PERIOD2蛋白积累速率可靠地预测了心律失常的自发发作。我们得出的结论是，单个SCN神经元可以产生昼夜节律振荡。然而，没有证据表明细胞自主起搏器具有特殊的或解剖学上的局部分类。相反，这些结果表明AVP，VIP和其他SCN神经元是内在的但不稳定的生物钟振荡器，它们依赖于网络交互来稳定其原本嘈杂的循环。

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