MODULATION OF TRANSIENT OUTWARD POTASSIUM CURRENT BY GTP, CALCIUM, AND GLUTAMATE IN HORIZONTAL CELLS OF THE XENOPUS-RETINA

被引:12
作者
AKOPIAN, A
WITKOVSKY, P
机构
[1] NYU, MED CTR, DEPT PHYSIOL, NEW YORK, NY 10016 USA
[2] NYU, MED CTR, DEPT BIOPHYS, NEW YORK, NY 10016 USA
关键词
D O I
10.1152/jn.1994.71.5.1661
中图分类号
Q189 [神经科学];
学科分类号
071006 ;
摘要
1. Membrane currents of luminosity horizontal cells (L-HCs) and chromatic horizontal cells (C-HCs) isolated from the Xenopus retina were characterized using the whole-cell patch-clamp technique. 2. The current-voltage curve for the L-HC had a characteristic negative slope conductance in the voltage range of -30 to -10 mV that was not evident in the C-HC. 3. A transient outward 4-aminopyridine-sensitive potassium current (A-current) was the most prominent current in C-HCs but was also present in L-HCs. A-current characteristics in the two horizontal cell (HC) classes were closely similar. Its threshold of activation was above -45 mV. The half-voltage of inactivation was close to -70 mV. The decay of the A-current was lit by a single exponential with time constants of 30 and 40 ms at depolarizing voltage steps to -10 and +30 mV, respectively. 4. The voltage for 50% A-current inactivation shifted toward negative potentials shortly after we established the whole-cell configuration. This shift was changed to more positive potentials by internal application of guanosine 5'-triphosphate, resulting in a significant overlap of A-current activation and inactivation functions near -40 mV, which is well within the normal operating range of the HC.
引用
收藏
页码:1661 / 1671
页数:11
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