Nelson R, Kolb H, Freed M A
Laboratory of Neurophysiology, National Institute of Neurological Diseases and Stroke, National Institutes of Health, Bethesda, Maryland 20892.
J Comp Neurol. 1993 Mar 1;329(1):68-84. doi: 10.1002/cne.903290106.
Six OFF-alpha ganglion cells and a single OFF-beta ganglion cell were penetrated with intracellular microelectrodes and marked with horseradish peroxidase (HRP) in a perfused cat eyecup. Gaussian center radii (Rc) ranging from 40 to 217 microns were measured for receptive fields mapped with slits, values in agreement with previous extracellular reports. ON and OFF response components revealed nearly identical Rc's and center locations. Although Gaussian diameters (2Rc) were about 80% of dendritic field diameters overall, in this sample dendritic and receptive fields were not well correlated. Spatial tuning of ganglion cells was evidenced in peaked amplitude-vs.-width functions, fit by difference-of-Gaussians models. Such plots yielded Rc values about 40% less than position-vs amplitude plots. Rs values for surrounds ranged from 200 to 1,700 microns. Rod and cone signals were investigated with flicker. Rod flicker signals in OFF-alpha cells were larger and of shorter latency than in either horizontal or AII amacrine cells. Cone flicker signals were also short in latency, with an ON response time constant of 9 msec, and an OFF response time constant of 3 msec. The OFF-alpha rod-cone transition involved a latency increase of 20-30 msec. The spontaneous and light-evoked impulse rates of OFF-alpha responses varied linearly with extrinsic current, but the amplitude of ON hyperpolarization was little affected. After injection of staining current, the OFF-beta cell transiently depolarized at ON, suggestive of ON inhibition with reversed chloride gradient, a result not seen in OFF-alpha responses. Events (peaked, depolarizing voltage fluctuations) of high, low, and intermediate amplitudes were studied in OFF-alpha responses. High amplitude events (impulses), were OFF-correlated with the stimulus, and exhibited mean rise times (transit time from 25 to 75% of peak amplitude) from 255 to 392 microseconds. Intermediate level events (presumed synaptic origin) were also OFF correlated and had longer rise times (325 microseconds to 1.56 microseconds). Low level events (234-685 microseconds) revealed either ON, ON/OFF, or not stimulus correlation.
在一个灌注猫眼杯标本中，用细胞内微电极刺入6个α-型开-关神经节细胞和1个β-型开-关神经节细胞，并以辣根过氧化物酶（HRP）进行标记。用狭缝映射感受野，测得高斯中心半径（Rc）范围为40至217微米，该值与之前的细胞外记录结果一致。开反应和关反应成分显示出几乎相同的Rc值和中心位置。虽然高斯直径（2Rc）总体上约为树突野直径的80%，但在这个样本中，树突野和感受野的相关性并不好。神经节细胞的空间调谐通过高斯差分模型拟合的峰-宽函数得到证实。这样的图得到的Rc值比位置-幅度图得到的值小约40%。周围区域的Rs值范围为200至1700微米。用闪烁刺激研究了视杆和视锥信号。α-型开-关细胞中的视杆闪烁信号比水平细胞或AII无长突细胞中的更大且潜伏期更短。视锥闪烁信号的潜伏期也很短，开反应时间常数为9毫秒，关反应时间常数为3毫秒。α-型开-关细胞从视杆到视锥的转换涉及潜伏期增加20 - 30毫秒。α-型开-关反应的自发冲动率和光诱发冲动率与外加电流呈线性变化，但开超极化的幅度受影响较小。注入染色电流后，β-型开-关细胞在开时短暂去极化，提示存在氯离子梯度反转的开抑制，这一结果在α-型开-关反应中未观察到。研究了α-型开-关反应中高、低和中等幅度的事件（峰值、去极化电压波动）。高幅度事件（冲动）与刺激呈关相关，平均上升时间（从峰值幅度的25%到75%的过渡时间）为255至392微秒。中等幅度事件（推测源于突触）也与关相关，上升时间更长（325微秒至1.56毫秒）。低幅度事件（234 - 685微秒）显示出关、开/关或与刺激无关。
