Immunohistochemistry in association with scanning electron microscopy for the morphological characterization and location of astrocytes of the rabbit retina

The purpose of the present investigation was to establish a method for the morphological characterization and location of the several types of astrocytes in the rabbit retina. Whole retinas were incubated with unlabeled antibody to glial fibrillary acidic protein (GFAP) and, afterwards, treated with secondary antibody labeled according to the requirements for the visualization of the antigen–antibody reaction either with the confocal or transmission electron microscope. Specimens treated similarly to the latter were osmium enhanced and analyzed with scanning electron microscopy (SEM). The different immunohistochemical approaches led to the conclusion that the cells selectively visualized with the SEM are astrocytes. The higher resolution and depth of focus of this instrument allowed a better morphological characterization and a more precise location of the astrocytes in the several levels of the inner portion of the rabbit retina. The method described herein, in which pre-embedding immunohistochemistry for GFAP on rabbit retinas was associated with osmium enhancement and examination with SEM, proved to be reliable and efficient for the morphological characterization and location of astrocytes.