University of Copenhagen, Department of Neuroscience and Pharmacology, Panum Institute, Copenhagen, Denmark.
J Neurophysiol. 2010 May;103(5):2599-610. doi: 10.1152/jn.00668.2009. Epub 2010 Feb 17.
We have developed an in vivo model for intracellular recording in the adult anesthetized mouse using sharp microelectrode electrodes as a basis for investigations of motoneuron properties in transgenic mouse strains. We demonstrate that it is possible to record postsynaptic potentials underlying identified circuits in the spinal cord. Forty-one motoneurons with antidromic spike potentials (>50 mV) from the sciatic nerve were investigated. We recorded the intrinsic properties of the neurons, including input resistance (mean: 2.4 +/- 1.2 MOmega), rheobase (mean: 7.1 +/- 5.9 nA), and the duration of the afterhyperpolarization (AHP; mean: 55.3 +/- 14 ms). We also measured the minimum firing frequencies (F(min), mean 23.5 +/- 5.7 SD Hz), the maximum firing frequencies (F(max); >300 Hz) and the slope of the current-frequency relationship (f-I slope) with increasing amounts of current injected (mean: 13 +/- 5.7 Hz/nA). Signs of activation of persistent inward currents (PICs) were seen, such as accelerations of firing frequency or jumps in the membrane potential with increasing amounts of injected current. It is likely that the particular anesthetic regime with a mixture of Hypnorm and midazolam is essential for the possibility to evoke PICs. The data demonstrate that mouse spinal motoneurons share many of the same properties that have been demonstrated previously for cat, rat, and human motoneurons. The shorter AHP duration, steeper f-I slopes, and higher F(min) and F(max) than those in rats, cats, and humans are likely to be tailored to the characteristics of the mouse muscle contraction properties.
我们开发了一种在体模型，用于使用锋利的微电极在麻醉的成年小鼠中进行细胞内记录，作为研究转基因小鼠品系中运动神经元特性的基础。我们证明了在脊髓中记录识别电路下的突触后电位是可能的。从坐骨神经记录了 41 个具有逆行尖峰电位（>50 mV）的运动神经元。我们记录了神经元的固有特性，包括输入电阻（平均值：2.4 ± 1.2 MOmega）、阈强度（平均值：7.1 ± 5.9 nA）和后超极化（AHP；平均值：55.3 ± 14 ms）的持续时间。我们还测量了最小放电频率（F(min)，平均值 23.5 ± 5.7 SD Hz）、最大放电频率（F(max)；>300 Hz）以及随着注入电流增加而变化的电流-频率关系（f-I 斜率）（平均值：13 ± 5.7 Hz/nA）。观察到持久内向电流（PICs）激活的迹象，例如随着注入电流的增加而增加放电频率或膜电位跳跃。很可能是混合使用 Hypnorm 和咪达唑仑的特定麻醉方案对于引发 PICs 是必要的。这些数据表明，小鼠脊髓运动神经元具有许多与猫、大鼠和人类运动神经元之前证明的相同特性。与大鼠、猫和人类相比，较短的 AHP 持续时间、更陡峭的 f-I 斜率以及更高的 F(min)和 F(max)可能是针对小鼠肌肉收缩特性量身定制的。
