EFFECT OF CHANGES IN INTRACELLULAR AND EXTRACELLULAR-SODIUM ON THE INWARD (ANOMALOUS) RECTIFICATION IN SALAMANDER PHOTORECEPTORS
EFFECT OF CHANGES IN INTRACELLULAR AND EXTRACELLULAR-SODIUM ON THE INWARD (ANOMALOUS) RECTIFICATION IN SALAMANDER PHOTORECEPTORS
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DOI：
10.1113/jphysiol.1984.sp015086
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发表时间：
1984-01-01
影响因子：
5.5
通讯作者：
BERTRAND, D
中科院分区：
文献类型：
--
作者：
BADER, CR;BERTRAND, D
用酶解法对虎蝾螈视网膜进行分离，得到了孤立杆状内节。利用膜片移液管的单移液管电压钳技术研究了膜超极化激活的内向电流Ih。为了在电压依赖性的K和Ca电流中分离研究Ih，必须用含有TEA[四乙基铵]和Co的溶液进行过量使用。当膜片移液管中的溶液含有45 mM KCl和50 mM NaCl时，Ih的特征与之前用细尖微电极描述的特征无法区分：逆转电位在-30 mV附近，Ih被细胞外铯阻断，并因细胞外K浓度的增加而增强。当细胞外钾浓度升高时，观察到Ih的增加是由于电导和驱动力的增加。膜片移液器中N的替换，细胞外Na的替换使Ih的逆转电位位移至-74 mV，该值在孤立内段的K平衡电位范围内。细胞内或细胞内和细胞外的Na取代既不影响Ih的激活范围，也不影响最大电导。第3-6点表明，Ih主要（如果不是完全）由Na和K携带，并且负责Ih的通道对细胞内或细胞外钠浓度的修饰不敏感。长期超极化、部分含碳阻滞和全氮取代的结果与Na和K渗透同一类型通道的结果一致。
Solitary rod inner segments were obtained by enzymic dissociation of the tiger salamander retina. Ih, an inward current activated by membrane hyperpolarization, was studied using the single-pipette voltage-clamp technique with patch pipettes. In order to investigate Ih in isolation from voltage-dependent K and Ca currents, it was necessary to superfuse with a solution containing TEA [tetraethylammonium] and Co. When the solution in the patch pipette contained 45 mM KCl and 50 mM NaCl, the characteristics of Ih were indistinguishable from those previously described with fine-tip microelectrodes: the reversal potential was near -30 mV and Ih was blocked by extracellular caesium and enhanced by an increase in the extracellular K concentration. The increase in Ih observed when the extracellular K concentration is raised is due to an increase in conductance and in driving force. Replacement of N in the patch pipettes, replacement of extracellular Na displaced the reversal potential for Ih to -74 mV, a value in the range of the K equilibrium potential in solitary inner segments. Intracellular or intra- and extracellular Na substitution affected neither the activation range of Ih nor the maximum conductance. Points 3-6 showed that Ih is carried mainly, if not exclusively, by Na and K and that the channel responsible for Ih is insensitive to modifications of the intra- or extracellular sodium concentration. The results of long-term hyperpolarization, of partial block with Cs and of total N substitution are consistent with Na and K permeating the same type of channel.