Receptive field of the retinal bipolar cell: A pharmacological study in the tiger salamander
Receptive field of the retinal bipolar cell: A pharmacological study in the tiger salamander
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DOI：
10.1152/jn.1996.76.3.2005
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发表时间：
1996-09-01
影响因子：
2.5
通讯作者：
Owen, WG
中科院分区：
文献类型：
--
作者：
Hare, WA;Owen, WG
1. 人们普遍认为，视网膜双极细胞周围感受野的信号通过gaba能突触从水平细胞传递到双极细胞。为了验证这一观点，我们将γ -氨基丁酸（GABA）激动剂和拮抗剂应用于分离的、灌注的娃娃鱼（Ambystoma tigrinum）视网膜，同时记录双极细胞、水平细胞和光感受器的细胞内情况。正如我们之前报道的那样，GABA类似物d -氨基戊酸与微毒素一起施用不会阻断水平细胞反应或双极细胞的中心反应，但会阻断中心和非中心双极细胞的周围反应。GABA(A)拮抗剂picrotoxin或bicuculline、GABA(B)激动剂baclofen或GABA(B)拮抗剂phaclofen、GABA(C)拮抗剂picrotoxin或顺式-4-氨基营养酸均未阻断环绕反应。这些药物联合使用同样无效。GABA本身在水平细胞中激活了强大的GABA摄取机制，而nipecotic酸是一种竞争性激动剂。在水平细胞和双极细胞中，它还激活了GABAA的大电导，这种电导可以分流光反应，但可以被微毒素或二环霉素阻断。与微毒素一起施用GABA以阻断GABA(A)激活的分流效应，但在浓度足以使已知类型的GABA受体饱和时，并不能消除双极细胞周围反应。甘氨酸或其拮抗剂士的宁，或同时消除gaba能和甘氨酸能途径的药物组合，都不能阻断环绕反应。虽然我们不能完全排除一种新的氨基丁酸能突触的参与，但对我们的发现最简单的解释是，介导双极细胞周围的主要途径既不是氨基丁酸能也不是甘氨酸能。
1. It is widely believed that signals contributing to the receptive field surrounds of retinal bipolar cells pass from horizontal cells to bipolar cells via GABAergic synapses. To test this notion, we applied gamma-aminobutyric acid (GABA) agonists and antagonists to isolated, perfused retinas of the salamander Ambystoma tigrinum while recording intracellularly from bipolar cells, horizontal cells, and photoreceptors.2. As we previously reported, administration of the GABA analogue D-aminovaleric acid in concert with picrotoxin did not block horizontal cell responses or the center responses of bipolar cells but blocked the surround responses of both on-center and off-center bipolar cells.3. Surround responses were not blocked by the GABA(A) antagonists picrotoxin or bicuculline, the GABA(B) agonist baclofen or the GABAB antagonist phaclofen, and the GABA(C) antagonists picrotoxin or cis-4-aminocrotonic acid. Combinations of these drugs were similarly ineffective.4. GABA itself activated a powerful GABA uptake mechanism in horizontal cells for which nipecotic acid is a competitive agonist. It also activated, both in horizontal cells and bipolar cells, large GABAA conductances that shunted light responses but that could be blocked by picrotoxin or bicuculline.5. GABA, administered together with picrotoxin to block the shunting effect of GABA(A) activation, did not eliminate bipolar cell surround responses at concentrations sufficient to saturate the known types of GABA receptors.6. Surround responses were not blocked by glycine or its antagonist strychnine, or by combinations of drugs designed to eliminate GABAergic and glycinergic pathways simultaneously.7. Although we cannot fully discount the involvement of a novel GABAergic synapse, the simplest explanation of our findings is that the primary pathway mediating the bipolar cell's surround is neither GABAergic nor glycinergic.