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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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Citing This Article：

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).