The ionic dependence of voltage-activated inward currents in the pharyngeal muscle of Caenorhabditis elegans
The ionic dependence of voltage-activated inward currents in the pharyngeal muscle of Caenorhabditis elegans
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DOI：
10.1007/s10158-006-0018-y
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发表时间：
2006-06-01
影响因子：
--
通讯作者：
Holden-Dye, Lindy
中科院分区：
文献类型：
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作者：
Vinogradova, Irina;Cook, Alan;Holden-Dye, Lindy
秀丽隐杆线虫的咽部由一个由径向定向的肌肉细胞组成的合胞体组成，这些肌肉细胞同步地、有节奏地收缩，以摄入和粉碎细菌，并将它们泵入动物的肠道。支持这种活动的动作电位表面上与脊椎动物心脏动作电位相似，具有长时间的钙依赖平台期。虽然咽肌在没有外部钙离子的情况下可以产生动作电位，但当钠从细胞外溶液中去除时，动作电位就不存在了（Franks et al. 2002）。在这里，我们使用了来自咽部的全细胞膜片钳记录，并显示了低电压激活的内向电流，这些电流存在于零外部钙离子中，并在零外部钠离子中减少。鉴于已知的电压门控钙通道对钠离子的渗透性，当钠离子存在时，零钙缺乏效果并不奇怪。，当钙离子存在时，零钠电流的减少很难用传统的电压门控钙通道来解释。egl-19 （n582）在咽l型钙通道中具有功能缺失突变，也记录了向内电流，这些电流在零外钠条件下也显着减少。尽管这种明显依赖于外部钠离子，但电流被镉、钡和镍等二价阳离子部分阻断。使用单通道记录，我们确定了一个阳离子通道，其开放时间持续时间通过去极化而增加。在由内向外的贴片中，对称钠溶液中的单通道电导最高。需要进一步的研究来确定这些通道对咽动作电位的贡献。
The pharynx of Caenorhabditis elegans consists of a syncytium of radially orientated muscle cells that contract synchronously and rhythmically to ingest and Crush bacteria and PUMP them into the intestine of the animal. The action potentials that support this activity are superficially similar to vertebrate cardiac action potentials in appearance with a long, calcium-dependent plateau phase. Although the pharyngeal muscle can generate action potentials in the absence of external calcium ions, action potentials Lire absent when sodium is removed from the extracellullar solution (Franks et al. 2002). Here we have used whole cell patch clamp recordings from the pharynx and show low voltage-activated inward currents that are present in zero external calcium and reduced in zero external sodium ions. Whilst the lack of effect of zero calcium when sodium ions are present is not surprising in view of the known permeability of voltage-gated calcium channels to sodium ions., the reduction in Current in zero sodium when calcium ions are present is harder to explain In terms of a conventional voltage-gated calcium channel. Inward Currents were also recorded from egl-19 (n582) which has a loss of function mutation in the pharyngeal L-type calcium channel and these were also markedly reduced in zero external sodium. Despite this apparent dependence on external sodium Ions, the Current was partially blocked by the divalent cations, cadmium, barium and nickel. Using single-channel recordings we identified a cation channel for which the open-time duration was increased by depolarisation. In inside-out patches, the single-channel conductance was highest in symmetrical sodium solution. Further studies are required to determine the contribution of these channels to the pharyngeal action potential.