Sensitivity and kinetics of mouse rod flash responses determined in vivo from paired-flash electroretinograms
Sensitivity and kinetics of mouse rod flash responses determined in vivo from paired-flash electroretinograms
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DOI：
10.1111/j.1469-7793.1999.0593v.x
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发表时间：
1999-04-15
影响因子：
5.5
通讯作者：
Pepperberg, DR
中科院分区：
文献类型：
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作者：
Hetling, JR;Pepperberg, DR
1.记录角膜的视网膜电图（ERG）。C57 BL/8J小鼠使用配对闪光程序，其中在时间0的短暂测试闪光之后在时间t（探测）是固定强度的明亮探测闪光，并且其中在时间t = t（探测）+6ms确定探测响应幅度。分析在一系列配对闪光试验中获得的探测响应以导出A（t），一个振幅族，它代表视杆细胞感光器对测试闪光的集体反应。主要目的是获得归一化导出响应A（t）/A（mo）的数学描述，作为I-测试（测试闪光强度）的函数。2.对于固定的tprobe（80 ≤ t（probe）≤ 1200 ms），A（t）/A（mo）由饱和指数函数[1-exp（-k（t）I（test））]描述，其中k（t）是时间依赖性灵敏度参数。对于t = 86 ms，A（t），k（86）峰值附近的时间为7.0 +/-1.2（暗视艾德s m（-2））（-1）（平均值+/-S.D.; n = 4）。根据以下公式分析A（t）/A（mo）数据，该公式是上述指数函数的时间广义形式，其中（k（86）I（试验））被乘积[k（86）I（试验）u（t）]代替，其中u（t）与试验闪光强度无关。函数u（t）被建模为比例因子γ、激活项{1-exp [-alpha（t-t（d））（2）]}和衰减项exp的乘积（-t/tau（ω））：A（t）A（mo）= 1-exp [-k（86）I（test）u（t）]; u（t）= gamma {1-exp [-alpha（t-t（d））（2）]} exp（-t/τ（ω）），其中t（d）是短暂的延迟，τ（ω）是指数时间常数，并且α表征激活项的加速度。对于高达2.57暗视艾德s m（-2）的I-检验，A（t）的总体时程可通过上述公式进行良好描述，其中伽马= 2.21，t（d）= 3.1 ms，τ（ω）= 132 ms，α = 2.32 x 10（-4）ms（-2）。α的近似减半改善了上述方程对ERG a波和在t约0 - 20 ms获得的A（t）/A（mo）数据的拟合。A（t）的动力学和灵敏度特性表明，它近似于棒对测试闪光的体内聚集光电流响应，并意味着上述方程中的u（t）是单位（即单光子）响应的近似动力学描述。
1. Electroretinograms (ERGs) were recorded corneally from. C57BL/8J mice using a paired-flash procedure in which a brief test flash at time zero was followed at time t(probe) by a bright probe flash of fixed strength, and in which the probe response amplitude was determined at time t = t(probe) + 6 ms. Probe responses obtained in a series of paired-flash trials were analysed to derive A(t), a family of amplitudes that putatively represents the massed response of the rod photoreceptors to the test flash. A central aim was to obtain a mathematical description of the normalized derived response A (t)/A(mo) as a function of I-test, the test flash strength.2. With fixed tprobe (80 less than or equal to t(probe) less than or equal to 1200 ms), A(t)/A(mo) was described by the saturating exponential function [1 - exp(-k(t)I(test))], where k(t) is a time-dependent sensitivity parameter. For t = 86 ms, a time near the peak of A(t), k(86) was 7.0 +/- 1.2 (scotopic ed s m(-2))(-1) (mean +/- S.D.; n = 4).3. A(t)/A(mo) data were analysed in relation to the equation below, a time-generalized form of the above exponential function in which (k(86)I(test)) is replaced by the product [k(86)I(test)u(t)], and where u(t) is independent of the test flash strength. The function u(t) was modelled as the product of a scaling factor gamma, an activation term {1 - exp[-alpha(t - t(d))(2)]}, and a decay term exp(- t/tau(omega)):A(t)A(mo) = 1 - exp[-k(86)I(test)u(t)]; u(t) = gamma{1 - exp[-alpha(t - t(d))(2)]}exp(-t/tau(omega)),where t(d) is a brief delay, tau(omega) is an exponential time constant, and a characterizes the acceleration of the activation term. For I-test up to similar to 2.57 scotopic ed s m(-2), the overall time course of A(t) was well described by the above equation with gamma = 2.21, t(d) = 3.1 ms, tau(omega) = 132 ms and alpha = 2.32 x 10(-4) ms(-2). An approximate halving of alpha improved the fit of the above equation to ERG a-wave and A(t)/A(mo) data obtained at t about 0-20 ms.4. Kinetic and sensitivity properties of A(t) suggest that it approximates the in vivo massed photocurrent response of the rods to a test flash, and imply that u(t) in the above equation is the approximate kinetic description of a unit, i.e. single photon, response.