Stiefel Klaus M, Gutkin Boris S, Sejnowski Terrence J
Howard Hughes Medical Institute, The Salk Institute for Biological Studies, La Jolla, California, United States of America.
PLoS One. 2008;3(12):e3947. doi: 10.1371/journal.pone.0003947. Epub 2008 Dec 16.
Spike generation in cortical neurons depends on the interplay between diverse intrinsic conductances. The phase response curve (PRC) is a measure of the spike time shift caused by perturbations of the membrane potential as a function of the phase of the spike cycle of a neuron. Near the rheobase, purely positive (type I) phase-response curves are associated with an onset of repetitive firing through a saddle-node bifurcation, whereas biphasic (type II) phase-response curves point towards a transition based on a Hopf-Andronov bifurcation. In recordings from layer 2/3 pyramidal neurons in cortical slices, cholinergic action, consistent with down-regulation of slow voltage-dependent potassium currents such as the M-current, switched the PRC from type II to type I. This is the first report showing that cholinergic neuromodulation may cause a qualitative switch in the PRCs type implying a change in the fundamental dynamical mechanism of spike generation.
皮层神经元中动作电位的产生取决于多种内在电导率之间的相互作用。相位响应曲线（PRC）是衡量膜电位扰动引起的动作电位时间偏移的指标，它是神经元动作电位周期相位的函数。在阈强度附近，纯正向（I型）相位响应曲线与通过鞍结分岔产生的重复放电起始有关，而双相（II型）相位响应曲线则指向基于霍普夫 - 安德罗诺夫分岔的转变。在皮层切片中对第2/3层锥体神经元的记录中，胆碱能作用与M电流等慢电压依赖性钾电流的下调一致，将PRC从II型转换为I型。这是首次报道表明胆碱能神经调制可能导致PRC类型的定性转换，这意味着动作电位产生的基本动力学机制发生了变化。
