Andrade da Costa B L, de Mello F G, Hokoç J N
Departamento de Fisiologia e Farmacologia, UFPE, Recife, Brazil.
Brain Res. 2000 Apr 28;863(1-2):132-42. doi: 10.1016/s0006-8993(00)02111-9.
The release of GABA from amacrine and interplexiform cells after exposure to excitatory amino acids (EAAs) agonists was investigated by immunohistochemistry. Cebus monkey retinas were treated in vitro with 50 microM kainate (KA) or 5 mM L-Glutamate (L-Glu), for 30 min at 37 degrees C. The effects of the EAAs were measured by detecting immunocytochemically the GABA remaining in the tissue after stimulation. L-Glu and KA reduced the number of GABA-immunoreactive perikarya in the innermost part of the inner nuclear layer by approximately 60% and 80%, respectively, as compared to controls. The cell processes in the inner plexiform layer (IPL) were restricted to only three defined bands in the strata 1, 3 and 5, as compared to an intense and homogeneous labeling in the IPL of the untreated retinas. The effect of KA was inhibited by 100 microM CNQX, 100 microM NNC-711, or when Na(+) was replaced by choline. The release of GABA was Ca(2+)-independent, suggesting the mobilization of GABA from the cytoplasmic pool of this neurotransmitter. At least two subsets of retinal neurons including amacrine and interplexiform cells retained GABA-immunoreactivity after stimulation with EAAs, as revealed by glutamic acid decarboxylase (GAD) immunocytochemistry. Our results suggest that non-NMDA receptor activation by KA and glutamate are associated with the efflux of GABA from cells of the inner retina (amacrine and interplexiform cells). The data also show that cells containing GAD-67 released GABA via its transporter, while cells containing exclusively GAD-65 apparently did not release the neurotransmitter by the reversal of the transporter.
通过免疫组织化学研究了暴露于兴奋性氨基酸（EAA）激动剂后无长突细胞和网间细胞释放GABA的情况。将僧帽猴视网膜在体外于37℃用50微摩尔/升的海人酸（KA）或5毫摩尔/升的L-谷氨酸（L-Glu）处理30分钟。通过免疫细胞化学检测刺激后组织中剩余的GABA来测量EAA的作用。与对照组相比，L-Glu和KA分别使内核层最内层中GABA免疫反应性胞体的数量减少了约60%和80%。与未处理视网膜的内网状层（IPL）中强烈且均匀的标记相比，IPL中的细胞突起仅局限于第1、3和5层的三个明确带。KA的作用被100微摩尔/升的CNQX、100微摩尔/升的NNC-711抑制，或者当Na(+)被胆碱取代时也被抑制。GABA的释放不依赖Ca(2+)，表明GABA从这种神经递质的细胞质池中动员出来。如谷氨酸脱羧酶（GAD）免疫细胞化学所显示，至少包括无长突细胞和网间细胞在内的两个视网膜神经元亚群在受到EAA刺激后仍保留GABA免疫反应性。我们的结果表明，KA和谷氨酸对非NMDA受体的激活与GABA从视网膜内层细胞（无长突细胞和网间细胞）的外流有关。数据还表明，含有GAD-67的细胞通过其转运体释放GABA，而仅含有GAD-65 的细胞显然不会通过转运体的逆转来释放神经递质。
