Density and types of calretinin-containing retinal ganglion cells in rabbit

- Single-cell injection after immunocytochemistry provides the functional anatomy.
- Subpopulations of retinal ganglion cells are immunoreactive for calretinin.
- Ten types of retinal ganglion cells express calretinin in rabbit.

Single-cell injection with lipophilic dyes following immunocytochemistry is extremely valuable for revealing the morphology of a cell expressing a protein of interest, and is a more reliable technique for cell type classification than standard morphological techniques. This study focuses on calretinin (CR), which is used as a selective marker for distinct subpopulations of neurons in the rabbit retina. The present study used single-cell injection after immunocytochemistry to describe the density and types of CR-containing retinal ganglion cells (RGCs) in rabbit. The density of CR-immunoreactive cells in the rabbit RGC cell layer was 426 cells/mm2. CR-containing RGCs were identified by immunocytochemistry and were then iontophoretically injected with a lipophilic dye, DiI. Subsequently, confocal microscope was used to characterize the morphology of CR-immunoreactive RGCs based on their dendritic field size, branching pattern, and stratification of the inner plexiform layer. Our results show that 10 morphologically different types of rabbit RGCs expressed CR. CR-containing RGCs were heterogeneous in their morphology. This approach to integrate the selective expression of a particular protein with spatial patterns of dendritic arborization will lead to a better understanding of RGCs.