IMMUNOCYTOCHEMICAL LOCALIZATION OF CALRETININ CONTAINING NEURONS IN RETINA FROM RABBIT, CAT, AND DOG

Calcium homeostasis is critical for many neuronal functions, yet the d istribution of calcium-binding protein is not always conserved among s pecies, even between closely related species. We decided therefore to study the distribution of one of these calcium-binding proteins calret inin, in retina from rabbit, cat, and dog. Calretinin was localized us ing antibody immunocytochemistry. Calretinin immunoreactivity was foun d in numerous cell bodies in the ganglion cell layer in all three anim als. These cells had small to medium-sized somas. Large ganglion cells , however? were not labeled using antiserum against calretinin. In the inner nuclear layer, calretinin immunoreactivity was found in many ne urons in all three species. The regular distribution of neurons, the i nner marginal location of their cell bodies in the inner nuclear layer , and the distinctive bilaminar morphologies of their dendritic arbors in the inner plexiform layer suggested that these calretinin-positive cells were AII amacrine cells. Calretinin immunoreactivity was observ ed in both A- and B-type horizontal cells in cat and dog retina. Howev er. horizontal cells in the rabbit retina were not labeled by this ant ibody. Neurons in the photoreceptor cell layer were not labeled by thi s antibody. The present study suggests that calretinin immunoreactivit y is present in several populations in the retina. In particular, calr etinin labels AII amacrine cells and a subpopulation of ganglion cells in all three animals. Horizontal cells, however, were not labeled in rabbit. (C) 1998 Elsevier Science Ireland Ltd. All rights reserved.