Zhang Ai-Jun, Zhang Jian, Wu Samuel M
Cullen Eye Institute, Baylor College of Medicine, Houston, Texas 77030, USA.
J Comp Neurol. 2006 Nov 20;499(3):422-31. doi: 10.1002/cne.21117.
Light responses, dendritic/axonal morphology, receptive field diameters, patterns of dye coupling, and relative rod/cone inputs of various types of horizontal cells (HCs) were studied using intracellular recording and Lucifer yellow/neurobiotin dye injection methods in the flatmount tiger salamander retina. Three physiologically and morphologically distinct types of HC entities were identified. 1) The A-type HCs are somas that do not bear axons, with average (+/-SE) soma diameters of 20.01 +/- 0.59 microm, relatively sparse and thick dendrites, and they resemble the A-type HC in mammals. The average receptive field diameter of these cells is 529.6 +/- 10.87 microm and they receive inputs predominantly from cones. 2) The B-type HCs are broad-field somas that bear thin and long axons, with average soma diameters of 17.67 +/- 0.38 microm, thinner dendrites of higher density, and they resemble the B-type HC in mammals. The average receptive field diameter of these cells is 1,633.55 +/- 37.34 microm and they receive mixed inputs from rods and cones. 3) The B-type HC axon terminals are broad-field, coarse axon terminal processes and they resemble the B-type HC axon terminal in rabbits. The average receptive field diameter of these axon terminals is 1,291.67 +/- 24.02 microm and they receive mixed inputs from rods and cones. All these types of HC are dye-coupled with adjacent HCs of the same type. Additionally, B-type HCs and axon terminals are dye-coupled with subpopulations of bipolar cells whose axon terminals ramify in the proximal half of the inner plexiform layer, raising the possibility that these HCs may send feedforward antagonistic surround responses to depolarizing bipolar cells through electrical synapses.
在平铺的虎蝾螈视网膜中,使用细胞内记录和路西法黄/神经生物素染料注射方法,研究了不同类型水平细胞(HCs)的光反应、树突/轴突形态、感受野直径、染料偶联模式以及相对视杆细胞/视锥细胞输入。鉴定出了三种生理和形态上不同的HC实体类型。1)A型HCs是没有轴突的胞体,平均(±SE)胞体直径为20.01±0.59微米,树突相对稀疏且粗壮,它们类似于哺乳动物中的A型HC。这些细胞的平均感受野直径为529.6±10.87微米,主要接收来自视锥细胞的输入。2)B型HCs是具有细长轴突的宽视野胞体,平均胞体直径为17.67±0.38微米,树突较细且密度较高,它们类似于哺乳动物中的B型HC。这些细胞的平均感受野直径为1,633.55±37.34微米,接收来自视杆细胞和视锥细胞的混合输入。3)B型HC轴突终末是宽视野、粗大的轴突终末过程,类似于兔中的B型HC轴突终末。这些轴突终末的平均感受野直径为1,291.67±24.02微米,接收来自视杆细胞和视锥细胞的混合输入。所有这些类型的HC都与同类型的相邻HC染料偶联。此外,B型HCs和轴突终末与轴突终末在内网状层近端一半分支的双极细胞亚群染料偶联,这增加了这些HCs可能通过电突触向去极化双极细胞发送前馈拮抗周边反应的可能性。