非洲爪蟾卵细胞膜去极化后由超极化激活的瞬间内向电流

以双微电极电压钳制技术研究了未成熟非洲爪蟾卵细胞膜的离子流，发现在较长时间的去极化（－３０ｍｖ，５秒）前脉冲后由超极化引出的一个内向电流，其潜伏期约为０．５秒，经过０．４秒左右到达高峰，随近经０．８秒左右完全回复。其幅值随超极化程度增强而增大，其翻转电位接近氯平衡电位，并随胞外ＣＬ－浓度改变而变化。降低胞外ＣＬ－浓度使其幅值增大。降低胞外Ｎａ＾＋浓度对其无明显影响，提示此内几电流可能是氯离子流。以

TRANSIENT INWARD CONDUCTANCE IN THE XEN OPUS OOCYTE ACTIVATED BY HYPERPOLARIZATION SUBSEQUENT TO DEPOLARIZATION

Ionic current were studied in immature fully grown Xenojuts oocytes by using the microelec-trode voltage-clamp technique. An inward current was induced by a hyperpolarizing voltage step subsequent to a long-lasting depolarization prepulse. This current occurred with a latency of about 0. 5s after the beginning of the hyperpolarizing step,and then fully developed within 0. 4s,and subsequently subsided completely in 0. 8s. As the hyperpolarizing command potential was increas- ing,the amplitude of the current increased. The reversal potential of the current is closed to the equilibrium potential of the chloride and was chant.ed with the external chloride concentration. As the external chloride concentration was lowered markedly,the amplitude of the current increased. As the external sodium concentration was lowered, however, the current was reduced slightly only. It is indicated that this current was mainly carried by chloride. Replacement of calcium with barium in the external solution increased the current,and the reversal potential of the current is far from the equiiibriurr, potential of the potassium,both these facts suggested that this was not a potassium current. 8- Br -cAMP-a membrane permeable cAMP analog, which increased the intercellular cAMP level, might increase the current when it was added into the bath solution. This suggestes that this current was sensitive to the intercellular cAMP level.