Morphology And Distribution Of Bullfrog Retinal Müller Cells And Their Expression Of γ-aminobutyric Acid Transporters, Glutamate Transporter EAAC1 And Metabotropic Glutamate Receptors

M(u|¨)ller cells are the principal retinal glia. It was long thought that these specialized glial cells just play general supporting and nourishing roles in the retina. However, owing to the development and application of many new techniques (such as purified cell culture method, intracellular calcium image and patch clamp recording technique and so on), accumulating evidence suggests that M(u|¨)ller cells are more complex than previously thought. There may exist two-way communications between M(u|¨)ller cells and retinal neurons. M(u|¨)ller cells may modulate neuronal activity in the retina either through regulating the concentration of neuroactive substances in extracellular space or by modifying neuronal microenvironment. Thus, M(u|¨)ller cells play an active, dynamic role in the retinal function. The large size and easy accessibility make the M(u|¨)ller cells of the amphibian retina an ideal preparation in studies of glial cells. In the present work, the morphology and distribution of M(u|¨)ller cells and their expression of γ-aminobutyric acid transporters, glutamate transporter EAAC1 and metabotropic glutamate receptors were investigated in bullfrog retina preparation using immunofluorescence double labeling, confocal laser scanning microscopy, Western blotting and whole-cell recording on retinal slice techniques.Part One: Morphology and distribution of bullfrog retinal M(u|¨)ller cellsThe localization of glial fibrillary acidic protein (GFAP) immunoreactive glial cells in bullfrog retina was investigated through fluorescent immunohistochemistry and confocal laser scanning microscopy. We found that the monoclonal antibody against GFAP seems to label the entire population of M(u|¨)ller cells, and their main trunks, major processes and branchlets were delicately labeled. The results demonstrated that GFAP is a specific marker for bullfrog retinal M(u|¨)ller cells. Thus, this result provides an ideal tool to study in situ the retinal M(u|¨)ller cells morphologically or to identify M(u|¨)ller cells both in vivo and in vitro. Up to now, nothing is known about the distribution of amphibian M(u|¨)ller cells, so the morphology and distribution of adult bullfrog M(u|¨)ller cells was studied using the monoclonal antibody against GFAP as a probe of M(u|¨)ller cells. Several features of bullfrog M(u|¨)ller cell organization are noted. First, M(u|¨)ller cells are fairly uniform and distribute evenly, and...