The University of Texas at San Antonio, One UTSA Circle, BSB 1.03.14, San Antonio, TX 78249, United States.
J Neurosci Methods. 2017 Sep 1;289:23-30. doi: 10.1016/j.jneumeth.2017.06.018. Epub 2017 Jun 28.
The phase resetting curve (PRC) is a primary measure of a rhythmically firing neuron's responses to synaptic input, quantifying the change in phase of the firing oscillation as a function of the input phase. PRCs provide information about whether neurons will synchronize due to synaptic coupling or shared input. However, PRC estimation has been limited to in vitro preparations where stable intracellular recordings can be obtained and background activity is minimal, and new methods are required for in vivo applications.
We estimated PRCs using dense optogenetic stimuli and extracellular spike recording. Autonomously firing neurons in substantia nigra pars reticulata (SNr) of Thy1-channelrhodopsin 2 (ChR2) transgenic mice were stimulated with random barrages of light pulses, and PRCs were determined using multiple linear regression.
The PRCs obtained were type-I, showing only phase advances in response to depolarizing input, and generally sloped upward from early to late phases. Secondary PRCs, indicating the effect on the subsequent ISI, showed phase delays primarily for stimuli arriving at late phases. Phase models constructed from the optogenetic PRCs accounted for a large fraction of the variance in ISI length and provided a good approximation of the spike-triggered average stimulus.
Compared to methods based on intracellular current injection, the new method sacrifices some temporal resolution. However, it should be much more widely applicable in vivo, because only extracellular recording and optogenetic stimulation are required.
These results demonstrate PRC estimation using methods suitable for in vivo applications.
相位重置曲线（PRC）是定量测量节律性放电神经元对突触输入响应的主要指标，它量化了放电振荡相位随输入相位的变化。PRC 提供了关于神经元是否会由于突触耦合或共享输入而同步的信息。然而，PRC 的估计一直受到限制，仅限于能够获得稳定的细胞内记录和最小背景活动的体外制剂，并且需要新的方法用于体内应用。
我们使用密集的光遗传学刺激和细胞外尖峰记录来估计 PRC。在 Thy1-通道视紫红质 2（ChR2）转基因小鼠的黑质网状部（SNr）中，自主放电神经元受到随机光脉冲的刺激，使用多元线性回归来确定 PRC。
获得的 PRC 是 I 型的，仅对去极化输入表现出相位提前，并且通常从早期到晚期向上倾斜。表示对随后的 ISI 影响的次要 PRC 主要表现为刺激到达晚期相位时的相位延迟。从光遗传学 PRC 构建的相位模型解释了 ISI 长度变化的很大一部分，并很好地近似了尖峰触发的平均刺激。
与基于细胞内电流注入的方法相比，新方法牺牲了一些时间分辨率。然而，它应该在体内更广泛地适用，因为只需要细胞外记录和光遗传学刺激。
这些结果证明了使用适合体内应用的方法进行 PRC 估计。
