Immunohistochemical localization of GABA-containing neurons during postnatal development of the rat retina.

The localization of neurons containing gamma-amino-butyric acid (GABA)-immunoreactivity has been studied in the rat retina during postnatal development. Two populations of GABA-positive cells were observed. The first was located in the inner layers of the retina, with the number of cells and their immunoreactivity increasing during development until adulthood. Previous studies in adult rat enabled identification of these cells as a subpopulation of amacrine cells. The second was located in the outer layers of the retina. These cells displayed a transient GABA labelling, with no immunoreactivity detectable after postnatal day 15. Their localization and morphology corresponded to calbindin D-27kDa-positive horizontal cells. It was concluded that the transient GABA-positive cells were horizontal cells.