Barnes-Davies Margaret, Barker Matthew C, Osmani Fatima, Forsythe Ian D
Department of Cell Physiology & Pharmacology, University of Leicester, PO Box 138, Leicester LE1 9HN, UK.
Eur J Neurosci. 2004 Jan;19(2):325-33. doi: 10.1111/j.0953-816x.2003.03133.x.
Principal neurons of the lateral superior olive (LSO) detect interaural intensity differences by integration of excitatory projections from ipsilateral bushy cells and inhibitory inputs from the medial nucleus of the trapezoid body. The intrinsic membrane currents active around firing threshold will form an important component of this binaural computation. Whole cell patch recording in an in vitro brain slice preparation was employed to study conductances regulating action potential (AP) firing in principal neurons. Current-clamp recordings from different neurons showed two types of firing pattern on depolarization, one group fired only a single initial AP and had low input resistance while the second group fired multiple APs and had a high input resistance. Under voltage-clamp, single-spiking neurons showed significantly higher levels of a dendrotoxin-sensitive, low threshold potassium current (ILT). Block of ILT by dendrotoxin-I allowed single-spiking cells to fire multiple APs and indicated that this current was mediated by Kv1 channels. Both neuronal types were morphologically similar and possessed similar amounts of the hyperpolarization-activated nonspecific cation conductance (Ih). However, single-spiking cells predominated in the lateral limb of the LSO (receiving low frequency sound inputs) while multiple-firing cells dominated the medial limb. This functional gradient was mirrored by a medio-lateral distribution of Kv1.1 immunolabelling. We conclude that Kv1 channels underlie the gradient of LSO principal neuron firing properties. The properties of single-spiking neurons would render them particularly suited to preserving timing information.
外侧上橄榄核（LSO）的主要神经元通过整合来自同侧浓密细胞的兴奋性投射和来自梯形体内侧核的抑制性输入来检测双耳强度差异。在放电阈值附近活跃的内在膜电流将构成这种双耳计算的重要组成部分。采用体外脑片制备中的全细胞膜片钳记录来研究调节主要神经元动作电位（AP）发放的电导。来自不同神经元的电流钳记录显示，去极化时存在两种发放模式，一组仅发放单个初始AP且输入电阻低，而第二组发放多个AP且输入电阻高。在电压钳下，单发放神经元显示出对树突毒素敏感的低阈值钾电流（ILT）水平显著更高。用树突毒素-I阻断ILT可使单发放细胞发放多个AP，表明该电流由Kv1通道介导。两种神经元类型在形态上相似，且具有相似数量的超极化激活非特异性阳离子电导（Ih）。然而，单发放细胞在LSO的外侧肢（接收低频声音输入）中占主导，而多发放细胞在内侧肢中占主导。这种功能梯度与Kv1.1免疫标记的中外侧分布相对应。我们得出结论，Kv1通道是LSO主要神经元发放特性梯度的基础。单发放神经元的特性使其特别适合保留时间信息。
