Horizontal cells in the chameleon retina

Using the Golgi method, we have identified three morphological types of horizontal cell (HC) in the chameleon retina. Type I is located at the level of the retinal fovea and has a dense dentritic tree occupying a circular area of 4-5 ?m. Type II is situated in the peripheral and central parts of the retina. Its dentritic tree ranges between 20 and 40 ?m in diameter, increasing from the central retina to the periphery. Type III is found in the peripheral most zones of the retina and has a dendritic field of scarce, elongated prolongations covering an area of 40-70 ?m. In all three types of HC described, we observed that some neurons show among their dendrites a longer prolongation ending in a pointed swelling that could be the cell axon. In addition, we used immunohistochemistry to analize the expression of several neurotransmitters that may be used by horizontal cells. Our results suggest that horizontal cells have: GABAergic-Ir negative. Glycinergic-Ir negative, Glutamatergic-Ir negative, and Aspartatergic-Ir positive properties. This latter aspect is mainly seen in the peripheral parts of the chameleon retina.