McGinley Matthew J, Oertel Donata
Department of Physiology, University of Wisconsin, 1300 University Avenue, Madison, WI 53706, USA.
Hear Res. 2006 Jun-Jul;216-217:52-63. doi: 10.1016/j.heares.2006.02.006. Epub 2006 May 2.
The three types of principal cells of the ventral cochlear nucleus (VCN), bushy, octopus, and T stellate, differ in the detection of coincidence among synaptic inputs. To explore the role of the action-potential-generation mechanism in the detection of coincident inputs, we examined responses to depolarizing currents that increased at varying rates. To fire an action potential, bushy cells, likely of the globular subtype, had to be depolarized faster than 4.8+/-2.8 mV/ms, octopus cells faster than 9.5+/-3.6 mV/ms, and T stellate cells fired irrespective of the rate of depolarization. The threshold rate of depolarization permitted definition of a time window over which depolarization could contribute to generating action potentials. This integration window differed between cell types. It was 5.3+/-1.8 ms for bushy cells and 1.4+/-0.3 ms for octopus cells. T Stellate cells fired action potentials in response to even slow depolarizations, showing that their integration window was unlimited so that temporal summation in these cells is limited by the time course of synaptic potentials. The rate of depolarization threshold in octopus and bushy cells was decreased by alpha-dendrotoxin while T stellate cells were largely insensitive to alpha-dendrotoxin indicating that low-voltage-activated K+ conductances (gKL) are important determinants of the integration window.
腹侧耳蜗核（VCN）的三种主要细胞类型，即浓密细胞、章鱼细胞和T星状细胞，在突触输入的同步检测方面存在差异。为了探究动作电位产生机制在同步输入检测中的作用，我们检测了对以不同速率增加的去极化电流的反应。为了激发动作电位，可能属于球状亚型的浓密细胞去极化速度必须快于4.8±2.8 mV/ms，章鱼细胞快于9.5±3.6 mV/ms，而T星状细胞的激发与去极化速率无关。去极化的阈值速率允许定义一个时间窗口，在此窗口内去极化可有助于产生动作电位。这种整合窗口在细胞类型之间有所不同。浓密细胞的整合窗口为5.3±1.8 ms，章鱼细胞为1.4±0.3 ms。T星状细胞即使对缓慢的去极化也会激发动作电位，这表明它们的整合窗口是无限的，因此这些细胞中的时间总和受突触电位的时间进程限制。α-树突毒素可降低章鱼细胞和浓密细胞的去极化阈值速率，而T星状细胞对α-树突毒素基本不敏感，这表明低电压激活的K+电导（gKL）是整合窗口的重要决定因素。
