Division of Pharmacology, National Institute of Health Sciences, Kawasaki City, Kanagawa 210-9501, Japan
eNeuro. 2021 May 5;8(3). doi: 10.1523/ENEURO.0515-20.2021. Print 2021 May-Jun.
Among all voltage-gated potassium (Kv) channels, Kv2 channels are the most widely expressed in the mammalian brain. However, studying Kv2 in neurons has been challenging because of a lack of high-selective blockers. Recently, a peptide toxin, guangxitoxin-1E (GxTX), has been identified as a specific inhibitor of Kv2, thus facilitating the study of Kv2 in neurons. The mammalian dorsal cochlear nucleus (DCN) integrates auditory and somatosensory information. In the DCN, cartwheel inhibitory interneurons receive excitatory synaptic inputs from parallel fibers conveying somatosensory information. The activation of parallel fibers drives action potentials in the cartwheel cells up to 130 Hz , and the excitation of cartwheel cells leads to the strong inhibition of principal cells. Therefore, cartwheel cells play crucial roles in monaural sound localization and cancelling detection of self-generated sounds. However, how Kv2 controls the high-frequency firing in cartwheel cells is unknown. In this study, we performed immunofluorescence labeling with anti-Kv2.1 and anti-Kv2.2 antibodies using fixed mouse brainstem slice preparations. The results revealed that Kv2.1 and Kv2.2 were largely present on the cartwheel cell body membrane but not on the axon initial segment (AIS) nor the proximal dendrite. Whole-cell patch-clamp recordings using mouse brainstem slice preparation and GxTX demonstrated that blockade of Kv2 induced failure of parallel fiber-induced action potentials when parallel fibers were stimulated at high frequencies (30-100 Hz). Thus, somatic Kv2 in cartwheel cells regulates the action potentials in a frequency-dependent manner and may play important roles in the DCN function.
在所有电压门控钾 (Kv) 通道中，Kv2 通道在哺乳动物大脑中表达最广泛。然而，由于缺乏高选择性的阻断剂，研究 Kv2 在神经元中的作用一直具有挑战性。最近，一种肽毒素，广蝎毒素-1E（GxTX），已被鉴定为 Kv2 的特异性抑制剂，从而促进了 Kv2 在神经元中的研究。哺乳动物的背侧耳蜗核 (DCN) 整合听觉和躯体感觉信息。在 DCN 中，轮状抑制性中间神经元接收来自传递躯体感觉信息的平行纤维的兴奋性突触输入。平行纤维的激活使轮状细胞中的动作电位达到 130Hz，轮状细胞的兴奋导致主要细胞的强烈抑制。因此，轮状细胞在单耳声音定位和自我产生声音的检测消除中起着至关重要的作用。然而，Kv2 如何控制轮状细胞的高频放电尚不清楚。在这项研究中，我们使用固定的小鼠脑干切片制备物，用抗 Kv2.1 和抗 Kv2.2 抗体进行免疫荧光标记。结果表明，Kv2.1 和 Kv2.2 主要存在于轮状细胞体膜上，但不存在于轴突起始段 (AIS) 或近端树突上。使用小鼠脑干切片制备物和 GxTX 进行全细胞膜片钳记录表明，阻断 Kv2 会导致平行纤维在高频（30-100Hz）刺激时诱导的动作电位失败。因此，轮状细胞中的体细胞 Kv2 以频率依赖的方式调节动作电位，可能在 DCN 功能中发挥重要作用。
