In vivo studies of signaling in rod pathways of the mouse using the electroretinogram
In vivo studies of signaling in rod pathways of the mouse using the electroretinogram
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DOI：
10.1016/j.visres.2004.09.002
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发表时间：
2004-12-01
期刊：
影响因子：
1.8
通讯作者：
Frishman, LJ
中科院分区：
文献类型：
--
作者：
Robson, JG;Maeda, H;Frishman, LJ
目的：（a）检查连接视杆细胞和视杆细胞双极细胞的突触机制中存在阈值的可能性，该阈值可以减少来自视杆细胞的连续噪声的传输，而不阻止任何显着比例的单光子响应的传输。 (b) 估计该阈值的水平以及它可以用来降低的连续噪声的幅度。 (c) 确定视杆到视杆双极细胞通路中阈值机制的位置。方法：在抑制视网膜内部成分以分离 PII（去极化双极细胞的反应）后，用氯胺酮/甲苯噻嗪麻醉暗适应小鼠，进行角膜视网膜电图记录。通过玻璃体内注射 GABA、TTX 或在 Cx36 KO 动物中通过压碎视神经并等待神经节细胞退化来实现抑制。结果：使用超导光刺激获得的分离 PII 的所有能量标度记录，每棒产生远少于 1 次光异构化 (R*)（0.01-0.2 R*/棒），基本上具有 相同的波形。更强的刺激会导致能量标度记录的峰值振幅降低（饱和度），而足够强的刺激会在单个视杆中产生多种异构化，从而导致响应潜伏期的缩短和早期能量标度振幅的增加（超线性）。孤立PII上升沿的形状随闪光能量的变化而变化，这与突触阈值的存在相一致，突触阈值的电平小于单光子信号幅度的十分之一，并且连续噪声的均方根幅度甚至更小。然而，当在峰值时测量时，PII 的幅度与刺激能量成比例地线性增加，从最低水平一直到平均 0.2 R*/rod。结论：在杆到杆双极细胞突触的输出处存在阈值非线性，可以有效地减少连续杆噪声的传输，而不显着影响单光子信号的传输。这种非线性不会影响棒路径在光子计数模式下有效运行的水平上的整体线性函数。 (C) 2004 Elsevier Ltd. 保留所有权利。
Purpose: (a) To examine the possibility that there is a threshold in the synaptic mechanism linking rods to rod bipolar cells that can reduce the transmission of continuous noise from the rods without blocking the transmission of any significant proportion of single-photon responses. (b) To estimate the level of this threshold and the amplitude of the continuous noise which it can serve to reduce. (c) To identify the location of the threshold mechanism in the rod to rod bipolar cell pathway.Methods: Corneal electroretinogram recordings were made from dark-adapted mice anesthetized with ketamine/xylazine after inner-retinal components had been suppressed to isolate PII, the response of depolarizing bipolar cells. Suppression was achieved by intravitreal injections of GABA, TTX, or in Cx36 KO animals by crushing the optic nerve and waiting for ganglion cells to degenerate.Results: All energy-scaled records of isolated PII obtained with ganzfeld stimuli that gave rise to much less than one photoisomerization (R*) per rod (0.01-0.2 R*/rod), had an essentially identical waveform. Stronger stimuli caused a reduction in the peak amplitude of energy-scaled records (saturation) and stimuli strong enough to produce multiple isomerizations in individual rods resulted in a shortening of the response latency and an increase of the energy-scaled amplitude at early times (supralinearity). The shape of the rising edge of isolated PII changed with flash energy in a way that was consistent with the existence of a synaptic threshold whose level was less than one tenth of the amplitude of single-photon signals and a continuous noise whose rms amplitude was even less than this. However, when measured at the time of the peak, the amplitude of PII increased linearly in proportion to stimulus energy from the very lowest levels up to the point where there was, on average, 0.2 R*/rod.Conclusions: There is a threshold nonlinearity operating at the output of the rod to rod bipolar cell synapse that can usefully reduce the transmission of continuous rod noise without significantly affecting the transmission of single-photon signals. This nonlinearity does not affect the overall linear function of the rod pathway at levels at which it is effectively operating in a photon-counting mode. (C) 2004 Elsevier Ltd. All rights reserved.