Ayoub G S, Lam D M
Vision Res. 1985;25(9):1187-93. doi: 10.1016/0042-6989(85)90032-x.
The endogenous amino acid content of intact retinas and isolated horizontal cells was measured by high performance liquid chromatography (HPLC). In both of these preparations, the concentration of gamma-aminobutyric acid (GABA) was approximately 2 mM. The endogenous GABA of the isolated horizontal cells was specifically released upon depolarization of the cells by elevated external K+ concentrations. This K+ induced release of endogenous GABA has two components. There is a saturable, Ca2+-dependent portion which predominates with small depolarizations, and a Ca2+-independent fraction which is linearly dependent upon the membrane potential of the horizontal cells. The data presented suggest the possibility of a dual scheme for the release of GABA from goldfish horizontal cells. The first is a Ca2+-dependent, conventional synaptic release; and the second a Na+-driven, carrier mediated release, which is linearly dependent upon the cellular membrane potential and functions in the absence of extracellular Ca2+.
通过高效液相色谱法（HPLC）测定完整视网膜和分离的水平细胞中的内源性氨基酸含量。在这两种制剂中，γ-氨基丁酸（GABA）的浓度约为2 mM。分离的水平细胞的内源性GABA在细胞因外部K⁺浓度升高而发生去极化时特异性释放。这种K⁺诱导的内源性GABA释放有两个成分。有一个饱和的、Ca²⁺依赖性部分，在小去极化时占主导，还有一个Ca²⁺非依赖性部分，它与水平细胞的膜电位呈线性相关。所呈现的数据表明金鱼水平细胞释放GABA可能存在双重机制。第一种是Ca²⁺依赖性的传统突触释放；第二种是Na⁺驱动的载体介导释放，它与细胞膜电位呈线性相关，且在细胞外无Ca²⁺的情况下起作用。
