Division of Neurobiology, Department Biology II, Ludwig-Maximilians-Universität München Munich, Germany ; Institute of Biology, Fachbereich Biologie, Chemie, Pharmazie, Freie Universität Berlin Berlin, Germany.
Front Neural Circuits. 2013 Jul 11;7:117. doi: 10.3389/fncir.2013.00117. eCollection 2013.
Neuronal membrane properties can largely vary even within distinct morphological cell classes. The mechanisms and functional consequences of this diversity, however, are little explored. In the medial superior olive (MSO), a brainstem nucleus that performs binaural coincidence detection, membrane properties at rest are largely governed by the hyperpolarization-activated inward current (Ih) which enables the temporally precise integration of excitatory and inhibitory inputs. Here, we report that Ih density varies along the putative tonotopic axis of the MSO with Ih being largest in ventral, high-frequency (HF) processing neurons. Also Ih half-maximal activation voltage and time constant are differentially distributed such that Ih of the putative HF processing neurons activate faster and at more depolarized levels. Intracellular application of saturating concentrations of cyclic AMP removed the regional difference in hyperpolarization-activated cyclic nucleotide gated (HCN) channel activation, but not Ih density. Experimental data in conjunction with a computational model suggest that increased Ih levels are helpful in counteracting temporal summation of phase-locked inhibitory inputs which is particularly prominent in HF neurons.
神经元的膜特性即使在不同的形态细胞类型中也会有很大的变化。然而，这种多样性的机制和功能后果还很少被探索。在内侧上橄榄核（MSO），一个执行双耳同时检测的脑干核团中，静息状态下的膜特性主要由超极化激活内向电流（Ih）控制，该电流使兴奋性和抑制性输入的时间精确整合成为可能。在这里，我们报告说，Ih 的密度沿着 MSO 的假定音调轴变化，在腹侧、高频（HF）处理神经元中最大。此外，Ih 的半最大激活电压和时间常数也存在差异分布，使得假定的 HF 处理神经元的 Ih 更快地激活，并且在更去极化的水平上激活。细胞内应用饱和浓度的环磷酸腺苷消除了超极化激活环核苷酸门控（HCN）通道激活的区域差异，但 Ih 密度没有差异。实验数据结合计算模型表明，增加 Ih 水平有助于抵消与相位锁定抑制性输入的时间总和，而这在 HF 神经元中尤为明显。
