Newman E A
Eye Research Institute, Boston, MA 02114.
Brain Res. 1989 Oct 2;498(2):308-14. doi: 10.1016/0006-8993(89)91109-8.
The effect of barium on Müller cell K+ conductance was evaluated in the tiger salamander using enzymatically dissociated cells and cells in situ (retinal slice and isolated retina). Barium effects were similar in both cases. In dissociated cells, 50 microM Ba2+ depolarized cells 14.7 mV and raised cell input resistance from a control value of 16.0 to 133 M omega. For cells in situ, 50 microM Ba2+ depolarized cells 6.9 mV and raised cell resistance from 12.5 to 50.4 M omega. At corresponding Ba2+ concentrations, the resistance of cells in situ was somewhat lower than was the resistance of dissociated cells, a phenomenon that may be due to the small degree of electrical coupling present between Müller cells in situ. There was a similar positive correlation between the magnitude of Ba2+-induced depolarization and input resistance in both dissociated cells and in situ cells. The magnitude of depolarizations generated by localized K+ ejections onto Müller cells was reduced substantially by Ba2+. These observations indicate that Ba2+ is an effective K+ channel blocker in Müller cells in situ as well as in enzymatically dissociated cells.
利用酶解细胞和原位细胞（视网膜切片和分离的视网膜），在虎螈中评估了钡对米勒细胞钾离子电导的影响。在这两种情况下，钡的作用相似。在解离细胞中，50微摩尔/升的钡离子使细胞去极化14.7毫伏，细胞输入电阻从对照值16.0兆欧提高到133兆欧。对于原位细胞，50微摩尔/升的钡离子使细胞去极化6.9毫伏，细胞电阻从12.5兆欧提高到50.4兆欧。在相应的钡离子浓度下，原位细胞的电阻略低于解离细胞的电阻，这种现象可能是由于原位米勒细胞之间存在的少量电耦合所致。在解离细胞和原位细胞中，钡离子诱导的去极化幅度与输入电阻之间存在相似的正相关。通过向米勒细胞局部喷射钾离子产生的去极化幅度被钡离子显著降低。这些观察结果表明，钡离子在原位米勒细胞以及酶解细胞中都是一种有效的钾离子通道阻滞剂。
