Masked excitatory crosstalk between the ON and OFF visual pathways in the mammalian retina
Masked excitatory crosstalk between the ON and OFF visual pathways in the mammalian retina
复制标题
DOI：
10.1113/jphysiol.2011.213371
复制
发表时间：
2011-09-15
影响因子：
5.5
通讯作者：
Bloomfield, Stewart A.
中科院分区：
文献类型：
--
作者：
Farajian, Reza;Pan, Feng;Bloomfield, Stewart A.
视觉系统的一个基本组织特征是将ON和OFF响应分离成平行流来表示光的增加和减少。然而，我们发现阻断gaba能抑制揭示了OFF α -神经节细胞（α - gcs）中强大的ON反应。这些ON反应与OFF α - gcs的经典OFF反应具有相同的中心介导结构，但在L-AP4破坏ON通路后被消除。实验表明，GABA(A)和GABA(C)受体都参与了这种ON反应的掩蔽抑制，它们位于双极细胞轴突末端的突触前抑制突触，也可能位于无突细胞树突上。由于OFF α - gcs的树突不能接收来自内丛状层（IPL）下层-b的ON双极细胞轴突终端的兴奋性输入，我们研究了与邻近无突细胞形成的间隙连接介导的电突触形成接收ON信号途径的可能性。我们发现，应用间隙结阻滞剂消除了OFF α - gcs中未被掩盖的ON响应，而经典的OFF响应仍然存在。此外，我们还发现，与OFF α - gcs偶联的无分泌细胞在IPL的两个下膜中显示过程，从而形成了一个可能的底物，用于接收和传递ON信号给OFF α - gcs。最后，使用多电极阵列，我们发现在兔和小鼠视网膜中超过三分之一的神经节细胞显示了隐藏的ON和OFF信号，这表明隐藏交叉兴奋在哺乳动物视网膜内部是一种普遍现象。
A fundamental organizing feature of the visual system is the segregation of ON and OFF responses into parallel streams to signal light increment and decrement. However, we found that blockade of GABAergic inhibition unmasks robust ON responses in OFF alpha-ganglion cells (alpha-GCs). These ON responses had the same centre-mediated structure as the classic OFF responses of OFF alpha-GCs, but were abolished following disruption of the ON pathway with L-AP4. Experiments showed that both GABA(A) and GABA(C) receptors are involved in the masking inhibition of this ON response, located at presynaptic inhibitory synapses on bipolar cell axon terminals and possibly amacrine cell dendrites. Since the dendrites of OFF alpha-GCs are not positioned to receive excitatory inputs from ON bipolar cell axon terminals in sublamina-b of the inner plexiform layer (IPL), we investigated the possibility that gap junction-mediated electrical synapses made with neighbouring amacrine cells form the avenue for reception of ON signals. We found that the application of gap junction blockers eliminated the unmasked ON responses in OFF alpha-GCs, while the classic OFF responses remained. Furthermore, we found that amacrine cells coupled to OFF alpha-GCs display processes in both sublaminae of the IPL, thus forming a plausible substrate for the reception and delivery of ON signals to OFF alpha-GCs. Finally, using a multielectrode array, we found that masked ON and OFF signals are displayed by over one-third of ganglion cells in the rabbit and mouse retinas, suggesting that masked crossover excitation is a widespread phenomenon in the inner mammalian retina.