Identification of parvalbumin-containing retinal ganglion cells in rabbit.

A calcium-binding protein, parvalbumin (PV), is widely distributed in the central nervous system and is expressed in the retinal neurons of various vertebrate species. The present study was aimed at describing the types and density of PV-containing retinal ganglion cells (RGCs) in rabbits by using single-cell injection after immunocytochemistry. PV-containing RGCs were first identified by immunocytochemistry and were then iontophoretically injected with a lipophilic dye, DiI. Subsequently, confocal microscopy was used to characterize the morphological classification of the PV-immunoreactive (IR) ganglion cells on the basis of their dendritic field size, branching pattern, and stratification within the inner plexiform layer. The results indicated that at least 8 morphologically different types of rabbit RGCs express PV. They were heterogeneous in terms of their morphology. The present study showed that the proportion of RGCs that contained PV was between 17% and 19% of the total number of ganglion cells. The density of PV-IR RGCs in the rabbit retina was 144 cells/mm(2). Also, it was found that PV was present in all cholinergic amacrine cells in the ganglion cell layer (GCL) and the inner nuclear layer (INL). This integrated approach of characterizing the cell morphology and the selective expression of a particular protein will lead to a better understanding of the properties of RGCs.