Horizontal cells of the carp retina: Golgi impregnation and Procion-Yellow injection

Application of two methods for the selective staining of neurons, Golgi impregnation and intracellular marking with Procion Yellow, has revealed the anatomical arrangements of the horizontal cells in the carp retina. There are two basic horizontal-cell types, those with axons and these without. The former can be subdivided into three groups on the basis of the pattern of branching of the dendrites. These three structural groups are also functionally distinct, as shown by the electrical recordings made during Procion-Yellow injection. The axons of these three types of cell project into the proximal part of the inner nuclear layer, where they expand to form morphologically indistinguishable terminals. Fine horizontal processes leave the surfaces of these axon terminals. The functional behavior of a terminal resembles that of the associated soma. The horizontal cells lacking axons vary in morphological appearance, but they are similar functionally.