结论:M1固有光敏视网膜神经节细胞(ipRGC)已知为非成像视觉功能(潜意识视觉)编码绝对光强度(辐照度),如昼夜节律光夹带和瞳孔光反射。尚不清楚M1细胞如何响应相对光强度(对比度)和图案化的视觉信号。本研究确定了M1细胞中一种特殊形式的对比敏感性(对比抑制),提示图案化视觉信号在调节非图像形成视觉中的作用,以及M1ipRGC在编码图像形成视觉线索中的潜在作用。该研究还揭示了由囊泡谷氨酸转运体3(vGluT3)无长突细胞介导的突触机制和视网膜回路,这些细胞是M1细胞对比反应抑制的基础。M1ipRGC亚型(M1a和M1b)被揭示,基于与vGluT3无长突细胞的突触连接,感受场属性,固有光敏感性和膜兴奋性,和形态特征,建议在离散的M1亚群中划分视觉任务。
■已知M1型ipRGC(固有光敏视网膜神经节细胞)编码环境光信号,用于非图像形成的视觉功能,例如昼夜节律光夹带和瞳孔光反射。这里,我们报道,小鼠视网膜中的M1细胞(M1a)亚群具有对比度抑制(sbc)触发功能,这是以前仅在介导成像视觉的神经节细胞中发现的感受野特性.使用光遗传学和双膜片钳技术,我们发现囊泡谷氨酸转运体3(vGluT3)(vGluT3)无长突细胞使甘氨酸能,但不是谷氨酸,突触特异性地连接到M1a细胞上。M1a细胞视觉诱发反应的时空和药理学特性与vGluT3细胞的感受野特征密切相关,提示vGluT3无长突细胞输入在塑造M1a细胞的sbc触发特征中的主要作用。我们发现M1细胞的其他亚群(M1b),没有收到直接的vGluT3单元格输入,缺少sbc触发器功能,在固有光响应方面与M1a细胞明显不同,膜兴奋性,感受场特征和形态特征。一起,结果揭示了一个视网膜回路,该回路使用sbc触发功能来调节辐照度编码,并可能将图像形成线索发送到大脑中的非图像形成视觉中心。
M1 intrinsically photosensitive retinal ganglion cells (ipRGCs) are known to encode absolute light intensity (irradiance) for non-image-forming visual functions (subconscious vision), such as circadian photoentrainment and the pupillary light reflex. It remains unclear how M1 cells respond to relative light intensity (contrast) and patterned visual signals. The present study identified a special form of contrast sensitivity (suppressed-by-contrast) in M1 cells, suggesting a role of patterned visual signals in regulating non-image-forming vision and a potential role of M1 ipRGCs in encoding image-forming visual cues. The study also uncovered a synaptic mechanism and a retinal circuit mediated by vesicular glutamate transporter 3 (vGluT3) amacrine cells that underlie the suppressed-by-contrast response of M1 cells. M1 ipRGC subtypes (M1a and M1b) were revealed that are distinguishable based on synaptic connectivity with vGluT3 amacrine cells, receptive field properties, intrinsic photo sensitivity and membrane excitability, and morphological features, suggesting a division of visual tasks among discrete M1 subpopulations.
The M1 type ipRGC (intrinsically photosensitive retinal ganglion cell) is known to encode ambient light signals for non-image-forming visual functions such as circadian photo-entrainment and the pupillary light reflex. Here, we report that a subpopulation of M1 cells (M1a) in the mouse retina possess the suppressed-by-contrast (sbc) trigger feature that is a receptive field property previously found only in ganglion cells mediating image-forming vision. Using optogenetics and the dual patch clamp technique, we found that vesicular glutamate transporter 3 (vGluT3) (vGluT3) amacrine cells make glycinergic, but not glutamatergic, synapses specifically onto M1a cells. The spatiotemporal and pharmacological properties of visually evoked responses of M1a cells closely matched the receptive field characteristics of vGluT3 cells, suggesting a major role of the vGluT3 amacrine cell input in shaping the sbc trigger feature of M1a cells. We found that the other subpopulation of M1 cells (M1b), which did not receive a direct vGluT3 cell input, lacked the sbc trigger feature, being distinctively different from M1a cells in intrinsic photo responses, membrane excitability, receptive-field characteristics and morphological features. Together, the results reveal a retinal circuit that uses the sbc trigger feature to regulate irradiance coding and potentially send image-forming cues to non-image-forming visual centres in the brain.