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首页> 外文期刊>Journal of Neurophysiology >Ionic currents of isolated retinal pacemaker neurons: projected daily phase differences and selective enhancement by a phase-shifting neurotransmitter.
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Ionic currents of isolated retinal pacemaker neurons: projected daily phase differences and selective enhancement by a phase-shifting neurotransmitter.

机译：离体视网膜起搏器神经元的离子流：预计的每日相差和相移神经递质的选择性增强。

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The eye of Aplysia expresses a robust circadian rhythm of neuronal activity. We dissociated the retinal cells in primary culture and studied isolated pacemaker neurons to identify ionic currents that may have roles in the circadian clock mechanism. Individual neurons were studied with perforated-patch whole cell recording techniques in current- and voltage-clamp modes. Pacemaker neurons had resting potentials near -40 mV and, if neurites had grown out, produced spontaneous action potentials in darkness at <1 Hz. Depolarizing current injections increased the rate of action potential firing. Hyperpolarizing current injections were followed by slowly decaying (1-3 s) afterhyperpolarizations. Four ionic currents were characterized under voltage-clamp, including a Ca current (I(Ca)), a voltage-gated potassium current (I(KV)), an A current (I(A)), and a hyperpolarization-activated Cl current (I(Cl)). I(Cl) was only seen using Cl(-)-filled electrodes when high concentrations of Cl- diffused from the electrodeand is therefore unlikely to be important under physiological conditions. The magnitude of I(KV) was significantly larger during the projected zeitgeber predawn phase than during the postdawn phase, whereas the magnitude of I(A) was constant at these circadian phases, suggesting that only I(KV) is controlled by the circadian clock. Serotonin increased I(KV) by 29%, consistent with reports that serotonin suppresses optic nerve activity and phase shifts the circadian rhythm recorded from the intact eye. The enhancement of I(KV) likely contributes to membrane hyperpolarization, and it may be required for phase shifting. The phase-dependent changes in I(KV) provide evidence that each retinal pacemaker neuron contains a circadian clock, but confirmation must await further recordings made from individual pacemaker neurons that are isolated completely from all other cells in primary culture. From the present experiments, it appears that I(KV) is controlled by the circadian clock, in part, and it may be a required element in the pathway that is activated during serotonin-induced phase shifts.
机译：Aplysia的眼睛表达了神经元活动的稳健的昼夜节律。我们在原代培养中分离了视网膜细胞，并研究了孤立的起搏器神经元，以识别可能在昼夜节律机制中起作用的离子电流。在电流钳位模式和电压钳位模式下，使用穿孔膜全细胞记录技术研究了单个神经元。起搏器神经元的静息电位接近-40 mV，如果神经突生长，在黑暗中<1 Hz时会产生自发动作电位。电流注入去极化提高了动作电位的发射率。超极化电流注入后，在超极化后缓慢衰减（1-3 s）。在电压钳制下表征了四个离子电流，包括Ca电流（I（Ca）），电压门控钾电流（I（KV）），A电流（I（A））和超极化激活的Cl电流（I（Cl））。当高浓度的Cl-从电极扩散时，只有使用充满Cl（-）的电极才能看到I（Cl），因此在生理条件下不太可能是重要的。在预计的Zeitgeber黎明前阶段，I（KV）的幅度比黎明后阶段要大得多，而在这些昼夜节律阶段，I（A）的幅度是恒定的，这表明只有I（KV）受昼夜节律的控制。 。 5-羟色胺使I（KV）增加29％，这与5-羟色胺抑制视神经活动并从完整的眼睛记录的昼夜节律相移的报道一致。 I（KV）的增强可能导致膜超极化，并且可能需要移相。 I（KV）的依赖于相位的变化提供了证据，表明每个视网膜起搏器神经元都包含一个昼夜节律时钟，但是必须等待进一步确认由单独的起搏器神经元做出的进一步录音，而这些录音已与原代培养中的所有其他细胞完全隔离。从本实验中，似乎I（KV）部分地由昼夜节律时钟控制，并且它可能是5-羟色胺诱导的相移过程中激活的通路中的必需元素。

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