Control of the generator current in solitary rods of the Ambystoma tigrinum retina.
Control of the generator current in solitary rods of the Ambystoma tigrinum retina.
复制标题
控制虎钝口螈视网膜孤杆中的发电机电流。
DOI：
10.1113/jphysiol.1984.sp015131
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发表时间：
1984
期刊：
影响因子：
--
通讯作者：
Tachibana,M
中科院分区：
文献类型：
--
作者：
MacLeish,PR;Schwartz,EA;Tachibana,M
用单微管电压箝位技术研究了单独蝾螈（Ambystoma tigrinum）杆状光感受器中被光抑制的电流，即产生电流。在用Co、Cs和TEA（四乙基铵）阻断内段电压和Ca激活电流的同时，测量了Ca、环GMP和电压的影响。通过将外部Ca浓度从1.5 mM降低到10微米，发电机电流增加了5倍以上。通过向外段注入Ca，可使发电机电流降低约1/2。EGTA的注入使发电机电流迅速增加了约2倍。停止注射后，增加迅速逆转。注射环GMP或8Br环GMP可使发生器电流增加5倍以上。注射质子、pH缓冲液比辛（N，N‐bis[2‐羟乙基]甘氨酸）或GMP不会改变发生器电流。发电机电流的电流-电压曲线受外部Co的影响：在3 mM - Co中，电流-电压曲线的负电阻在- 45 ~ - 90 mV之间；在0.1 mM - Co中，电流-电压曲线平行于- 45 ~ - 90 mV之间的电压轴。这种差异归因于Co的电压依赖性阻滞。通过降低内部或外部Ca浓度，或注射环GMP，可降低Co对阻滞作用的敏感性。当棒浸泡在含有7 - 100微米Ca的介质中时，阶跃去极化产生了与时间相关的电流下降。由于逆转电位保持不变，下降归因于失活。增加外用Ca浓度或注射环GMP可降低小鼠的失活程度。
THe current suppressed by light, the generator current, was studied in solitary salamander (Ambystoma tigrinum) rod photoreceptors with the single‐micropipette voltage‐clamp technique. The effects of Ca, cyclic GMP, and voltage were measured while voltage‐ and Ca‐activated currents of the inner segment were blocked with Co, Cs, and TEA (tetraethylammonium). The generator current was increased more than 5‐fold by lowering the external Ca concentration from 1.5 mM to 10 microM. The generator current could be decreased approximately 1/2 by injecting Ca into an outer segment. Injection of EGTA quickly increased the generator current approximately 2‐fold. After injection ceased, the increase was quickly reversed. The generator current could be increased more than 5‐fold by injecting cyclic GMP or 8Br‐cyclic GMP. Injection of protons, the pH buffer bicine (N,N‐bis[2‐hydroxyethyl]glycine), or GMP did not produce a change in the generator current. The current‐voltage curve for the generator current was influenced by external Co: in 3 mM‐Co the current‐voltage curve had a negative resistance between ‐45 and ‐90 mV; in 0.1 mM‐Co the current‐voltage curve paralleled the voltage axis between ‐45 and ‐90 mV. The difference is attributed to a voltage‐dependent block by Co. Susceptibility to the blocking action of Co was reduced by lowering internal or external Ca concentration, or by injecting cyclic GMP. When rods were bathed in a medium containing 7‐100 microM‐Ca, a step depolarization produced a time‐dependent decline in current. Because the reversal potential remained constant, the decline is attributed to an inactivation. The extent of inactivation was reduced by increasing the concentration of external Ca or injecting cyclic GMP.