KINETIC AND PHARMACOLOGICAL PROPERTIES DISTINGUISHING 3 TYPES OF CALCIUM CURRENTS IN CHICK SENSORY NEURONS
KINETIC AND PHARMACOLOGICAL PROPERTIES DISTINGUISHING 3 TYPES OF CALCIUM CURRENTS IN CHICK SENSORY NEURONS
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DOI：
10.1113/jphysiol.1987.sp016864
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发表时间：
1987-12-01
影响因子：
5.5
通讯作者：
TSIEN, RW
中科院分区：
文献类型：
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作者：
FOX, AP;NOWYCKY, MC;TSIEN, RW
1. 采用全细胞膜片钳技术研究了培养的背根神经节（d.r.g.）细胞中的钙电流。使用抑制 Na+ 和 K+ 电流以及 3-10 mM 外部 Ca2+ 或 Ba2+ 的实验条件，我们根据电压依赖性动力学和药理学区分了三种不同类型的钙电流（L、T 和 N）。 2. 组分 L 在相对正的测试电位 (t.p. > -10 mV) 下激活，并在 200 ms 去极化期间几乎没有失活。它在 -60 mV 的保持电位 (h.p.) 下完全重新启动，并且可以通过使用更去极化的 h.p. 进行隔离。 (-40 mV) 以灭活其他两种类型的钙电流。 3. 使用弱测试脉冲可以单独看到组件 T。它在高于 -70 mV 的正电势时开始激活，并在维持去极化期间快速且完全失活（时间常数，τ约 20-50 ms）。电流幅度和衰减率随着去极化的增强而增加，直到两者达到约 -40 mV 的最大值。当 h.p > -60 mV 时失活完成，并在 -60 至 -95 mV 之间逐渐消除。 4. N 组分在相对较强的去极化（t.p. > -20 mV）下激活，并以 50 至 110 ms 的时间常数衰减。在非常宽的保持电位范围内（h.p.在-40和-110 mV之间）消除失活。 5. 移液管溶液中含有 10 mM-EGTA，用 Ba2+ 代替 Ca2+ 作为电荷载体不会改变任何组分的活化或弛豫速率。然而，T 型通道对 Ca2+ 和 Ba2+ 的渗透性大致相同，而 L 型和 N 型通道对 Ba2+ 的渗透性则大得多。 6. N 成分不能用 L 电流的电流依赖性失活来解释，该失活是由于在负保持电位下招募额外的 L 型通道而导致的：将外部 Ba2+ 浓度提高到 110 mM 会大大增加由 h.p. 引起的 L 电流的幅度。 = - 30 mV，但产生很少的失活。7。镉离子 (20-50 μM) 实际上消除了 N 和 L 电流（> 90% 阻断），但 T 相对不受影响（< 50% 阻断）。 200μM-Cd2+阻断所有三种成分。 8.镍离子(100μ)强烈降低T电流，但N和L电流几乎没有变化。 9.二氢吡啶拮抗剂硝苯地平(10μM)以保持电位抑制L电流(约60％阻断)，使一半L型通道失活。它不会降低保持电位下的 T 或 N 电流，从而产生类似程度的失活。 10. Ω-毒素组分GVIA (Ω-CgTX VIA)，一种来自地纹芋螺毒液的肽，用于产生持久的N和L电流阻断。以这种方式分离的 T 电流的特性与动力学分析推断的一致。
1. Calcium currents in cultured dorsal root ganglion (d.r.g.) cells were studied with the whole-cell patch-clamp technique. Using experimental conditions that suppressed Na+ and K+ currents, and 3-10 mM-external Ca2+ or Ba2+, we distinguished three distinct types of calcium currents (L, T and N) on the basis of voltage-dependent kinetics and pharmacology. 2. Component L activates at relatively positive test potentials (t.p. > -10 mV) and shows little inactivation during a 200 ms depolarization. It is completely reprimed at a holding potential (h.p.) of -60 mV, and can be isolated by using a more depolarized h.p. (-40 mV) to inactivate the other two types of calcium currents. 3. Component T can be seen in isolation with weak test pulses. It begins activating at potentials more positive than -70 mV and inactivates quickly and completely during a maintained depolarization (time constant, .tau. .apprx. 20-50 ms). The current amplitude and the rate of decay increase with stronger depolarizations until both reach a maximum at approximately -40 mV. Inactivation is complete at h.p > -60 mV and is progressively removed between -60 and -95 mV. 4. Component N activates at relatively strong depolarizations (t.p. > -20 mV) and decays with time constants ranging from 50 to 110 ms. Inactivation is removed over a very broad range of holding potentials (h.p. between -40 and -110 mV). 5. With 10 mM-EGTA in the pipette solution, substitution of Ba2+ for Ca2+ as the charge carrier does not alter the rates of activation or relaxation of any component. However, T-type channels are approximately equally permeable to Ca2+ and Ba2+, while L-type and N-type channels are both much more permeable to Ba2+. 6. Component N cannot be explained by current-dependent inactivation of L current resulting from recruitment of extra L-type channels at negative holding potentials: raising the external Ba2+ concentration to 110 mM greatly increases the amplitude of L current evoked from h.p. = - 30 mV but produces little inactivation.7. Cadmium ions (20-50 .mu.M) virtually eliminate both N and L currents (> 90% block) but leave T relatively unaffected (< 50% block). 200 .mu.M-Cd2+ blocks all three components. 8. Nickel ions (100 .mu.) strongly reduce T current but leave N and L current little changed. 9. The dihydropyridine antagonist nifedipine (10 .mu.M) inhibits L current (.apprx. 60% block) at a holding potential that inactivates half the L-type channels. It does not reduce T or N currents at holding potentials that produce similar degrees of inactivation. 10. .omega.-Toxin fraction GVIA (.omega.-CgTX VIA), a peptide from the venom of Conus geographus was used to produce long-lasting block of N and L currents. Properties of T currents isolated in this manner agree with those inferred from kinetic analysis.