Dallas Mark L, Atkinson Lucy, Milligan Carol J, Morris Neil P, Lewis David I, Deuchars Susan A, Deuchars Jim
School of Biomedical Sciences, Worsley Building, University of Leeds, Leeds LS2 9NQ, UK.
J Physiol. 2005 Feb 1;562(Pt 3):655-72. doi: 10.1113/jphysiol.2004.073338. Epub 2004 Nov 4.
The voltage-gated potassium channel subunit Kv3.1 confers fast firing characteristics to neurones. Kv3.1b subunit immunoreactivity (Kv3.1b-IR) was widespread throughout the medulla oblongata, with labelled neurones in the gracile, cuneate and spinal trigeminal nuclei. In the nucleus of the solitary tract (NTS), Kv3.1b-IR neurones were predominantly located close to the tractus solitarius (TS) and could be GABAergic or glutamatergic. Ultrastructurally, Kv3.1b-IR was detected in NTS terminals, some of which were vagal afferents. Whole-cell current-clamp recordings from neurones near the TS revealed electrophysiological characteristics consistent with the presence of Kv3.1b subunits: short duration action potentials (4.2 +/- 1.4 ms) and high firing frequencies (68.9 +/- 5.3 Hz), both sensitive to application of TEA (0.5 mm) and 4-aminopyridine (4-AP; 30 mum). Intracellular dialysis of an anti-Kv3.1b antibody mimicked and occluded the effects of TEA and 4-AP in NTS and dorsal column nuclei neurones, but not in dorsal vagal nucleus or cerebellar Purkinje cells (which express other Kv3 subunits, but not Kv3.1b). Voltage-clamp recordings from outside-out patches from NTS neurones revealed an outward K(+) current with the basic characteristics of that carried by Kv3 channels. In NTS neurones, electrical stimulation of the TS evoked EPSPs and IPSPs, and TEA and 4-AP increased the average amplitude and decreased the paired pulse ratio, consistent with a presynaptic site of action. Synaptic inputs evoked by stimulation of a region lacking Kv3.1b-IR neurones were not affected, correlating the presence of Kv3.1b in the TS with the pharmacological effects.
电压门控钾通道亚基Kv3.1赋予神经元快速放电特性。Kv3.1b亚基免疫反应性（Kv3.1b-IR）广泛分布于延髓，在薄束核、楔束核和三叉神经脊束核中有标记神经元。在孤束核（NTS）中，Kv3.1b-IR神经元主要位于靠近孤束（TS）的位置，可能是γ-氨基丁酸能或谷氨酸能的。超微结构上，在NTS终末检测到Kv3.1b-IR，其中一些是迷走传入纤维。对TS附近神经元进行的全细胞电流钳记录显示出与Kv3.1b亚基存在相一致的电生理特性：动作电位持续时间短（4.2±1.4毫秒）和放电频率高（68.9±5.3赫兹），两者均对施加的四乙铵（0.5毫米）和4-氨基吡啶（4-AP；30微米）敏感。抗Kv3.1b抗体的细胞内透析模拟并阻断了四乙铵和4-AP对NTS和背柱核神经元的作用，但对迷走背核或小脑浦肯野细胞（它们表达其他Kv3亚基，但不表达Kv3.1b）无效。来自NTS神经元外向膜片的电压钳记录显示出一种外向钾电流，其基本特征与Kv3通道携带的电流相同。在NTS神经元中，电刺激TS诱发兴奋性突触后电位（EPSP）和抑制性突触后电位（IPSP），四乙铵和4-AP增加了平均幅度并降低了成对脉冲比率，这与突触前作用位点一致。刺激缺乏Kv3.1b-IR神经元的区域所诱发的突触输入不受影响，这将TS中Kv3.1b的存在与药理作用联系起来。
