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非洲爪蟾顶盖神经元的抑制性微突触后电流频率和振幅的电压依赖性

朱丹, 艾育德, 蔡浩然

北京大学第一医院中心实验室. 北京 100034；内蒙古医学院附属医院眼科. 内蒙古, 呼和浩特 010050

摘要

采用全细胞记录膜片钳技术，研究非洲爪蟾脑片视顶盖神经元微突触后电流(miniature inhibitory postsynaptic current, mIPSC)频率和振幅对电压依赖关系。观察到以下结果：当通过改变记录电极内的 DC电流，将神经元的膜电位从静息电位逐步(每步10 mV的增量)去极化或超极化时，mIPSC的频率和/或振幅分别升高或降低。随着膜电位的去极化，mIPSC的频率逐渐升高；当钳位电压升至+10 mV时，mIPSC的频率达到最高值。 当神经元去极化时，振幅仅轻微升高。膜电位去极化达到­--30 mV或­--40 mV时，mIPSC的振幅最大；进一步去极化，振幅反而下降。另外，在膜电位去极化至­--20 mV和+10 mV之间时，可记录到大的mIPSC。在无Ca~(2+)浸浴液中，mIPSC的频率和振幅也随膜电位的去极化而逐步增高，但频率的增高幅度远不如在生理盐水浸浴中增高幅度明显。 当浸浴液中[K~(+)]_(0)增高时，mIPSC的频率明显降低，而振幅轻微降低。当细胞外[K~(+)]_(0)浓度升高超过20 mmol/L时，神经元产生明显的缓慢内向或外向膜电流。mIPSC频率和振幅与膜电位存在依赖性的可能机制在文中作了简短的讨论。

关键词： 电压依赖性; 抑制性微突触后电流; 视顶盖神经元; 脑片; 去极化; 膜电位; 非洲爪蟾

Voltage-dependence of miniature inhibitory postsynaptic current frequency and amplitude in tectal neurons of Xenopus

Zhu Dan, Ai Yude, Tsai Haojan

Central Laboratory of the First Hospital, Peking University. Beijing 100034, China；Department of Ophthalmology of the Affiliated Hospital, Medical College of Inner Mongolia. Huhehot 010050, China

Abstract

Experiments were performed to study the voltage-dependence of miniature inhibitory postsynaptic current (mIPSC) frequency and amplitude using patch-clamp technique with whole cell recording in optic tectal slices of Xenopus. The following results have been observed. When the membrane potentials of a neuron were depolarized or hyperpolarized stepwise from a resting potential via recording pipette to inject a DC current, the frequency and/or amplitude of mIPSCs increased or decreased respectively. The frequency of mIPSCs increased gradually with depolarizing membrane potential and it attained to the maximum as the membrane potential was held at +10 mV. The amplitude increased slightly as the neuron was depolarized. When the depolarization of membrane potential reached -­30 or -­40 mV, the amplitudes of mIPSCs were maximal. Further depolarization resulted in a decrease of amplitude. Meanwhile, the large mIPSCs appeared when the membrane potential depolarized to a range between­ -20 mV and +10 mV. With Ca~(2+)-free bath solution, the frequency and amplitude of mIPSCs also increased stepwise progressively on depolarization of membrane potential, but the increase was less marked as corresponding value in normal saline perfusion. When the [K~(+)]_(0) in bath solution increased, the frequency of mIPSCs decreased markedly and the amplitude of mIPSCs decreased slightly. If the external K~(+) concentration increased further to higher than 20 mmol/L, the neuron produced a marked slow inward or outward membrane current. The possible mechanism underlying the voltage-dependence of mIPSC frequency and amplitude is discussed briefly.

Key words: Voltage-dependence;Miniature inhibitory postsynaptic current;Tectal neuron;Slice;Depolarization;membrane potential;Xenopus

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引用本文：

朱丹, 艾育德, 蔡浩然. 非洲爪蟾顶盖神经元的抑制性微突触后电流频率和振幅的电压依赖性[J]. 生理学报 2006; 58 (1): .

Zhu Dan, Ai Yude, Tsai Haojan. Voltage-dependence of miniature inhibitory postsynaptic current frequency and amplitude in tectal neurons of Xenopus. Acta Physiol Sin 2006; 58 (1): (in Chinese with English abstract).