Roles of aspartate and glutamate in synaptic transmission in rabbit retina. I. Outer plexiform layer.
Roles of aspartate and glutamate in synaptic transmission in rabbit retina. I. Outer plexiform layer.
复制标题
天冬氨酸和谷氨酸在兔视网膜突触传递中的作用。
DOI：
10.1152/jn.1985.53.3.699
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发表时间：
1985
影响因子：
2.5
通讯作者：
Dowling,JE
中科院分区：
文献类型：
--
作者：
Bloomfield,SA;Dowling,JE
细胞内记录是从兔子的灌注、分离的视网膜眼杯的水平和双极细胞获得的。将假定的神经递质天冬氨酸、谷氨酸和几种类似物添加到超融合物中，同时监测视网膜神经元的膜电位和光响应性。 L-天冬氨酸和L-谷氨酸都模仿内源性光感受器递质对水平细胞、双极细胞和非双极细胞的作用。在 2.5-20 mM 的应用浓度下，L-天冬氨酸和 L-谷氨酸的作用无法区分。 D-天冬氨酸增强了 L-天冬氨酸和 L-谷氨酸对水平细胞的作用。这表明这些氨基酸的主动摄取系统存在于兔视网膜的外丛状层（OPL）中。谷氨酸类似物红藻氨酸对二级神经元产生类似于天冬氨酸和谷氨酸的作用，但浓度低两个数量级以上。谷氨酸类似物使君子氨酸具有与红藻氨酸类似的作用，但效力要低得多。天冬氨酸类似物 n-甲基 DL-天冬氨酸 (NMDLA) 拮抗水平和非双极细胞上光感受器递质的作用。 NMDLA 的这种作用仅在低浓度（50 µM）下观察到。此外，NMDLA 可以阻断外源性红藻氨酸的作用。 NMDLA 对双极细胞没有明显影响。谷氨酸类似物 2-氨基-4-磷酸丁酸可逆地阻断双极细胞的反应，但对水平或非双极细胞反应没有影响。这表明双极细胞拥有独特的突触受体。天冬氨酸类似物2-氨基-3-膦酰基丙酸没有表现出这种选择性，表明这种独特的受体是谷氨酸偏好受体。拮抗剂α-谷氨酸甲酯、α-氨基己二酸和谷氨酸二乙酯均显示出较弱的拮抗二级神经元光感受器递质作用的能力。这项研究的结果表明，谷氨酸或谷氨酸样物质可能是兔子视网膜中视杆细胞和视锥细胞的递质。将目前的研究结果与之前在低等脊椎动物视网膜中获得的结果进行比较表明，所有脊椎动物视网膜的 OPL 的基本药理学设计非常相似。
Intracellular recordings were obtained from horizontal and bipolar cells of the superfused, isolated retina-eyecup of the rabbit. The putative neurotransmitters aspartate, glutamate, and several analogues were added to the superfusate while the membrane potential and light-responsiveness of the retinal neurons were monitored. Both L-aspartate and L-glutamate mimicked the actions of the endogenous photoreceptor transmitter on horizontal cells, on-bipolar cells, and off-bipolar cells. At applied concentrations of 2.5-20 mM, the actions of L-aspartate and L-glutamate were indistinguishable. D-aspartate potentiated the effects of both L-aspartate and L-glutamate on horizontal cells. This suggests that active uptake systems for these amino acids exist in the outer plexiform layer (OPL) of the rabbit retina. The glutamate analogue kainate produced effects similar to those of aspartate and glutamate on second-order neurons, but at concentrations lower by over two orders of magnitude. The glutamate analogue quisqualate had effects similar to kainate but with much less potency. The aspartate analogue n-methyl DL-aspartate (NMDLA) antagonized the effects of the photoreceptor transmitter on horizontal and off-bipolar cells. This action of NMDLA was only observed at low concentrations (50 microM). In addition, NMDLA could block the effects of exogenously applied kainate. The NMDLA had no clear effects on on-bipolar cells. The glutamate analogue 2-amino-4-phosphonobutyrate reversibly blocked the responses of on-bipolar cells but had no effect on either horizontal or off-bipolar cell responses. This suggests that on-bipolar cells possess a unique synaptic receptor. The aspartate analogue 2-amino-3-phosphonoproprionate did not show this selectivity, suggesting that this unique receptor is a glutamate-preferring receptor. The antagonists alpha-methyl glutamate, alpha-amino adipate, and glutamate diethyl ester all showed only a weak ability to antagonize the actions of the photoreceptor transmitter on second-order neurons. The results of this study indicate that glutamate or a glutamate-like substance is the likely transmitter of rods and cones in the rabbit retina. A comparison of the present findings with those previously obtained in lower vertebrate retinas suggests that the basic pharmacological design of the OPL of all vertebrate retinas is very similar.