The ON pathway rectifies the OFF pathway of the mammalian retina.
The ON pathway rectifies the OFF pathway of the mammalian retina.
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DOI：
10.1523/jneurosci.4733-09.2010
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发表时间：
2010-04-21
期刊：
影响因子：
--
通讯作者：
Freed MA
中科院分区：
文献类型：
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作者：
Liang Z;Freed MA
在脊椎动物的视觉系统中，开细胞对正对比度作出反应，关细胞对负对比度作出反应，因此开细胞和关细胞都表现出矫正。我们研究了开启通路纠正关闭通路的视网膜回路。将白色噪声投射到哺乳动物视网膜的体外制备物上，并在全细胞电压钳下从视网膜神经节细胞记录兴奋性电流。关闭细胞中的电流比开启细胞中的电流更整流：因此开启细胞中的电流能够发出阳性和阴性对比信号，但关闭细胞中的电流实际上仅限于阴性对比。阻断On通路中的信号使Off神经节细胞中的电流去整流，从而允许它们被正对比度调制，表明On通路通常整流Off神经节细胞中的电流。这种从On到Off途径的交叉整流需要完整的甘氨酸能抑制，这表明甘氨酸能无长突细胞，最有可能是AII无长突细胞，允许On双极细胞将Off双极细胞过度激活到接近递质释放阈值，从而整流Off神经节细胞中的兴奋性电流。开和关单元的不对称整流可以是对具有比以上更低于平均值的对比度水平的自然场景的适应。因此，为了使On和Off通路编码相同数量的对比度水平，On细胞必须发出一些负对比度的信号。
In the vertebrate visual system, On cells respond to positive contrasts and Off cells respond to negative contrasts, and thus both On and Off cells exhibit rectification. We investigated the retinal circuits by which the On pathway rectifies the Off pathway. White noise was projected onto an in vitro preparation of the mammalian retina and excitatory currents were recorded from retinal ganglion cells under whole cell voltage clamp. Currents in Off cells were more rectified than those in On cells: thus currents in On cells were able to signal both positive and negative contrasts but currents in Off cells were virtually restricted to negative contrasts. Blocking signals in the On pathway de-rectified currents in Off ganglion cells thus allowing them to be modulated by positive contrasts, indicating that the On pathway normally rectifies currents in Off ganglion cells. Such cross-rectification from On to Off pathways required intact glycinergic inhibition, indicating that a glycinergic amacrine cell, most likely the AII amacrine cell, allows the On bipolar cell to hyperpolarize the Off bipolar cell close to the threshold for transmitter release, thus rectifying excitatory currents in the Off ganglion cell. Asymmetrical rectification of On and Off cells may be an adaptation to natural scenes which have more contrast levels below the mean than above. Thus in order for On and Off pathways to encode an equal number of contrast levels, the On cells must signal some negative contrasts.