VOLTAGE-ACTIVATED AND CALCIUM-ACTIVATED CURRENTS STUDIED IN SOLITARY ROD INNER SEGMENTS FROM THE SALAMANDER RETINA
VOLTAGE-ACTIVATED AND CALCIUM-ACTIVATED CURRENTS STUDIED IN SOLITARY ROD INNER SEGMENTS FROM THE SALAMANDER RETINA
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DOI：
10.1113/jphysiol.1982.sp014372
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发表时间：
1982-01-01
影响因子：
5.5
通讯作者：
SCHWARTZ, EA
中科院分区：
文献类型：
--
作者：
BADER, CR;BERTRAND, D;SCHWARTZ, EA
通过对虎纹钝口螈（A. tigrinum）视网膜进行酶解分离，获得了单个视杆细胞内段。采用单电极电压钳技术研究了它们的膜电流。借助药物试剂分离出了单个电流。细胞外铯阻断了从 -30 mV超极化激活的一种电流。改变细胞外钠和钾的浓度会改变反转电位的值，其方式与该电流由两种离子等量携带相符。细胞外四乙铵（TEA）阻断了从 -70 mV去极化激活的一种电流。在正常介质中，这种电流的反转电位为 -72 mV。改变细胞外钾浓度会改变反转电位的值，其方式与该电流主要由钾携带相符。细胞外钴阻断了一种去极化激活的电流，该电流具有初始内向和后期外向成分。在将乙二醇双（β - 氨基 - 乙基醚） - N,N,N'',N'' - 四乙酸（EGTA）注入内段后，外向成分被抑制。然后钴阻断了一种内向电流。据信这种电流主要由钙携带。电导从 -45 mV去极化时增加，并在约0 mV达到最大值。在一个去极化阶跃之后，电流迅速激活（<20 ms），然后至少在几秒内保持恒定，没有失活的迹象。将铈注入内段消除了一种据信由P⁺携带的钙激活外向电流。在注入铈之后，还存在另一种钙激活电流，其反转电位为 -17 mV。改变细胞外氯浓度会改变反转电位的值，其方式与氯至少携带70%的电流相符。另一种阴离子可能携带剩余部分。当第2、3、5、6和7项中提到的5种电流被阻断时， -90到 -25 mV之间的膜电阻是线性的、与时间无关的，并且具有较高的值（2.1 GΩ）。这5种已确定的电流都可以在蝾螈视杆细胞正常工作的生理电压范围内被激活。
Solitary rod inner segments were obtained by enzymatic dissociation of the tiger salamander (A. tigrinum) retina. Their membrane currents were studied with the single-pipette voltage-clamp technique. Individual currents were isolated with the aid of pharmacological agents. Extracellular Cs blocked a current activated by hyperpolarization from -30 mV. Changing external Na and K concentrations altered the value of the reversal potential in a manner consistent with the current being carried equally by both ions. Extracellular tetraethylammonium (TEA) blocked a current activated by depolarization from -70 mV. In normal medium this current had a reversal potential of -72 mV. Changing the external K concentration altered the value of the reversal potential in a manner consistent with the current being carried predominantly by K. Extracellular Co blocked a current activated by depolarization that had an initial inward and a later outward component. After EGTA [ethylene glycol bis(.beta.-amino-ethyl ether)-N,N,N'',N''-tetraacetic acid] was injected into an inner segment the outward component was suppressed. Co then blocked an inward current. This current is believed to be carried predominantly by Ca. The conductance increased with depolarization from -45 mV and reached a maximum at .apprx. 0 mV. Following a step of depolarization the current activated rapidly (< 20 ms) and then remained constant for at least several seconds without evidence of inactivation. Injecting Ce into an inner segment eliminated a Ca activated outward current believed to be carried by P+. After the injection of Ce there remained another Ca-activated current with a reversal potential of -17 mV. Changing extracellular Cl concentration altered the value of the reversal potential in a manner consistent with Cl carrying at least 70% of the current. Another anion may carry the balance. When the 5 currents mentioned in items 2, 3, 5, 6 and 7 were blocked, the membrane resistance between -90 and -25 mV was linear, time-independent, and had a high value (2.1 G.OMEGA.). The 5 identified currents can all be activated in the physiological range of voltage in which salamander rods normally operate.