Dixon D B, Takahashi K, Copenhagen D R
Department of Ophthalmology, University of California, San Francisco 94143-0730.
Neuron. 1993 Aug;11(2):267-77. doi: 10.1016/0896-6273(93)90183-r.
Catfish horizontal cells exhibit a high voltage-activated, slowly inactivating calcium (HVA) current. In isolated cells, this current underlies a sustained action potential that can be evoked by depolarization. L-Glutamate at concentrations as low as 1 microM suppressed HVA current and shortened the duration of action potentials. pH indicator dye measurements revealed that L-glutamate acidified cells by up to 0.3 pH units. pH/HVA current dose-response curves indicated that the EC50 for pH inhibition of HVA current was 7.1 and the Hill coefficient was 1.98. L-Glutamate's suppression of HVA current was eliminated when the patch pipette solution contained a high concentration of proton buffer, but was not affected when pipettes contained GTP gamma S. These results support the hypothesis that L-glutamate can modulate HVA current by changing intracellular pH.
鲶鱼水平细胞表现出一种高电压激活、缓慢失活的钙（HVA）电流。在分离的细胞中，这种电流是持续动作电位的基础，该动作电位可由去极化诱发。低至1微摩尔浓度的L-谷氨酸抑制HVA电流并缩短动作电位的持续时间。pH指示剂染料测量显示，L-谷氨酸可使细胞酸化多达0.3个pH单位。pH/HVA电流剂量反应曲线表明，pH抑制HVA电流的EC50为7.1，希尔系数为1.98。当膜片钳微管溶液含有高浓度质子缓冲剂时，L-谷氨酸对HVA电流的抑制作用消除，但当微管含有GTPγS时不受影响。这些结果支持L-谷氨酸可通过改变细胞内pH来调节HVA电流这一假说。
