Gao Ming, Whitt Jessica L, Huang Shiyong, Lee Angela, Mihalas Stefan, Kirkwood Alfredo, Lee Hey-Kyoung
Solomon H. Snyder Department of Neuroscience, Zanvyl-Krieger Mind/Brain Institute, Johns Hopkins University, Baltimore, MD 21218, USA.
Department of Biology, University of Maryland, College Park, MD 20742, USA.
Philos Trans R Soc Lond B Biol Sci. 2017 Mar 5;372(1715). doi: 10.1098/rstb.2016.0156.
Synapses are intrinsically 'noisy' in that neurotransmitter is occasionally released in the absence of an action potential. At inhibitory synapses, the frequency of action potential-independent release is orders of magnitude higher than that at excitatory synapses raising speculations that it may serve a function. Here we report that the frequency of action potential-independent inhibitory synaptic 'noise' (i.e. miniature inhibitory postsynaptic currents, mIPSCs) is highly regulated by sensory experience in visual cortex. Importantly, regulation of mIPSC frequency is so far the predominant form of functional plasticity at inhibitory synapses in adults during the refractory period for plasticity and is a locus of rapid non-genomic actions of oestrogen. Models predict that regulating the frequency of mIPSCs, together with the previously characterized synaptic scaling of miniature excitatory PSCs, allows homeostatic maintenance of both the mean and variance of inputs to a neuron, a necessary feature of probabilistic population codes. Furthermore, mIPSC frequency regulation allows preservation of the temporal profile of neural responses while homeostatically regulating the overall firing rate. Our results suggest that the control of inhibitory 'noise' allows adaptive maintenance of adult cortical function in tune with the sensory environment.This article is part of the themed issue 'Integrating Hebbian and homeostatic plasticity'.
突触本质上是“嘈杂的”，因为在没有动作电位的情况下神经递质偶尔也会释放。在抑制性突触中，与动作电位无关的释放频率比兴奋性突触高几个数量级，这引发了人们对其可能具有某种功能的猜测。在此，我们报告视觉皮层中与动作电位无关的抑制性突触“噪声”（即微小抑制性突触后电流，mIPSCs）的频率受到感觉经验的高度调节。重要的是，到目前为止，mIPSC频率的调节是成年期可塑性不应期内抑制性突触功能可塑性的主要形式，并且是雌激素快速非基因组作用的一个位点。模型预测，调节mIPSCs的频率，连同先前表征的微小兴奋性PSC的突触缩放，能够使神经元输入的均值和方差进行稳态维持，这是概率性群体编码的一个必要特征。此外，mIPSC频率调节在稳态调节整体放电率的同时，能够保留神经反应的时间特征。我们的结果表明，对抑制性“噪声”的控制能够使成年皮层功能与感觉环境相协调地进行适应性维持。本文是主题为“整合赫布可塑性和稳态可塑性”的特刊的一部分。
