Transient Potassium Currents Regulate the Discharge Patterns of Dorsal Cochlear Nucleus Pyramidal Cells
Transient Potassium Currents Regulate the Discharge Patterns of Dorsal Cochlear Nucleus Pyramidal Cells
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DOI：
10.1523/jneurosci.19-06-02195.1999
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发表时间：
1999-03
期刊：
影响因子：
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通讯作者：
P. Kanold;P. Manis
中科院分区：
文献类型：
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作者：
P. Kanold;P. Manis
耳蜗背核（DCN）的锥体细胞对声音的反应有三种不同的时间放电模式：“暂停”、“积累”和“斩波”。类似的放电模式在体外观察到，并且取决于细胞去极化的电压。有人提出，失活A型K+电流（伊基）可能在产生这三种不同模式中起关键作用。在这项研究中，我们研究了DCN锥体细胞的瞬态电流的特性，以评估这一假设。在大鼠脑片（P11-P17）上，形态学鉴定的锥体细胞表现出三种电压依赖性放电模式。在锥体细胞的外向斑中存在两种失活电流：一种是对四乙铵（TEA）阻断不敏感的快速失活电流（IKIF，τ = 11 msec），另一种是对4-氨基吡啶（4-AP）阻断不敏感的快速失活电流（IKIS，τ = 145 msec），半失活电流接近− 85 mV。在34°C下失活的恢复由时间常数为10-30 msec的单指数描述，类似于第一尖峰潜伏期随超极化预脉冲持续时间增加的速率。急性分离的细胞也具有快速激活（22°C时<1 msec）的瞬态电流，在接近−45 mV时激活，在接近−80 mV时显示半失活。模型显示IKIF的去失活与放电模式相关。总的来说，快速失活K+电流的性质与其在塑造DCN锥体细胞放电模式中的作用一致。
Pyramidal cells in the dorsal cochlear nucleus (DCN) show three distinct temporal discharge patterns in response to sound: “pauser,” “buildup,” and “chopper.” Similar discharge patterns are seen in vitro and depend on the voltage from which the cell is depolarized. It has been proposed that an inactivating A-type K+ current (IKI) might play a critical role in generating the three different patterns. In this study we examined the characteristics of transient currents in DCN pyramidal cells to evaluate this hypothesis. Morphologically identified pyramidal cells in rat brain slices (P11–P17) exhibited the three voltage-dependent discharge patterns. Two inactivating currents were present in outside-out patches from pyramidal cells: a rapidly inactivating (IKIF, τ ∼11 msec) current insensitive to block by tetraethylammonium (TEA) and variably blocked by 4-aminopyridine (4-AP) with half-inactivation near −85 mV, and a slowly inactivating TEA- and 4-AP-sensitive current (IKIS, τ ∼145 msec) with half-inactivation near −35 mV. Recovery from inactivation at 34°C was described by a single exponential with a time constant of 10–30 msec, similar to the rate at which first spike latency increases with the duration of a hyperpolarizing prepulse. Acutely isolated cells also possessed a rapidly activating (<1 msec at 22°C) transient current that activated near −45 mV and showed half-inactivation near −80 mV. A model demonstrated that the deinactivation ofIKIF was correlated with the discharge patterns. Overall, the properties of the fast inactivating K+ current were consistent with their proposed role in shaping the discharge pattern of DCN pyramidal cells.