Calcium channels in Xenopus spinal neurons differ in somas and presynaptic terminals.
Calcium channels in Xenopus spinal neurons differ in somas and presynaptic terminals.
复制标题
非洲爪蟾脊髓神经元中的钙通道在体细胞和突触前末梢有所不同。
DOI：
10.1152/jn.2001.86.1.269
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发表时间：
2001
期刊：
影响因子：
--
通讯作者：
Brehm,P
中科院分区：
文献类型：
--
作者：
Li,W;Thaler,C;Brehm,P
钙通道通过促进膜去极化和允许钙离子进入，在细胞信号传导中发挥双重作用。爪蟾脊髓神经元胞体的钙和钙依赖性电流的膜片钳记录表明与突触前末梢的关键功能差异。终端和胞体均表现出显着的高压激活（HVA）钙电流，但只有胞体表现出额外的低压激活（LVA）T型电流。进一步的差异体现在 HVA 电流上； N型和R型通道在体细胞中占主导地位，而末端钙电流主要由N型通道组成，L型和R型通道的贡献较小。这些不同通道类型分布的潜在生理意义可能在于不同的通道动力学。体细胞 HVA 钙电流的激活比终端中的 HVA 电流发生得更慢。此外，体细胞 LVA 钙电流的激活和停用速度比任何 HVA 钙电流都要慢得多。快速激活和失活钙电流可能对于处理末梢的快速胞吐反应至关重要，而慢速 LVA 和 HVA 钙电流可能在塑造体细胞放电模式中发挥核心作用。为了支持这两个区室之间不同的动力学行为，我们发现体细胞钙电流激活了在终端记录中未观察到的显着的慢氯电流。该电流响应钙通过 LVA 或 HVA 通道进入而激活，并可能充当兴奋性或突触输入的调节器。这种通道类型对体细胞的限制进一步支持了以下观点：这些神经元中快速和慢速通道类型的差异表达是由体细胞和终末室的信号传导需求的差异决定的。
Calcium channels play dual roles in cell signaling by promoting membrane depolarization and allowing entry of calcium ions. Patch-clamp recordings of calcium and calcium-dependent currents from the soma ofXenopusspinal neurons indicate key functional differences from those of presynaptic terminals. Both terminals and somas exhibit prominent high-voltage-activated (HVA) calcium current, but only the soma expresses additional low-voltage-activated (LVA) T-type current. Further differences are reflected in the HVA current; N- and R-type channels are predominant in the soma while the terminal calcium current is composed principally of N type with smaller contribution by L- and R-type channels. Potential physiological significance for these different distributions of channel types may lie in the differential channel kinetics. Activation of somatic HVA calcium current occurs more slowly than HVA currents in terminals. Additionally, somatic LVA calcium current activates and deactivates much more slowly than any HVA calcium current. Fast-activating and -deactivating calcium current may be critical to processing the rapid exocytotic response in terminals, whereas slow LVA and HVA calcium currents may play a central role in shaping the somatic firing pattern. In support of different kinetic behavior between these two compartments, we find that somatic calcium current activates a prominent slow chloride current not observed in terminal recordings. This current activates in response to calcium entering through either LVA or HVA channels and likely functions as a modulator of excitability or synaptic input. The restriction of this channel type to the soma lends further support to the idea that differential expression of fast and slow channel types in these neurons is dictated by differences in signaling requirements for somatic and terminal compartments.