Immunolocalization of basic fibroblast growth factor and its receptor in adult goldfish retina.

The neural retina of teleost fish can regenerate following surgical or neurotoxic lesions. As a first attempt to uncover the factors important for the regenerative response, we used immunocytochemistry to demonstrate the presence of basic fibroblast growth factor (bFGF) and its receptor in the goldfish retina. The bFGF-immunoreactivity was present throughout the retina, but was most intense in photoreceptor cells, especially cones, and Müller glia. Immunoreactivity for the bFGF receptor was strongest in the axon terminals of photoreceptors, both rods and cones. This pattern of immunolocalization is especially interesting since the proliferating cells that are thought to be responsible for generating the neural regenerate are located among the photoreceptor axon terminals. These proliferating cells have been identified as rod precursors because in the intact retina they give rise only to rod photoreceptors. When the neural retina is damaged, however, rod precursors are thought to be the source of proliferating neuroepithelial cells responsible for generating the retinal regenerate. The role played by bFGF in normal neurogenesis, cell differentiation, and/or neuronal regeneration in the fish retina has yet to be determined.