Abstract
We describe here a procedure that significantly enhances the intensity and method-specificity of immunocytochemical staining in large mounted semi-thin plastic Epon sections. The procedure was developed for the detection of the neurotransmitter gamma-aminobutyric acid (GABA) in rat brain tissue fixed with glutaraldehyde, but it may also be helpful in unmasking other antigens under different conditions. In addition to some practical suggestions for improving the reproducibility of the staining procedure, we demonstrate that the crucial step in the procedure is pre-treatment of the deplasticized sections with proteinase-K before exposure to the first antibody. This leads to a high morphological resolution and an excellent immunocytochemical signal.