Simultaneous Golgi-Cox and immunofluorescence using confocal microscopy

Visualization of neuronal elements is of funda- mental importance in modern neuroscience. Golgi-Cox impregnation is a widely employed method that provides detailed information about morphological characteristics of neurons, but none regarding their neurochemical features. Immunocytochemical procedures, on the other hand, can provide a high degree of biochemical specificity but poorer morphological details, in particular if compared to Golgi- Cox impregnation. Hence, the combined use of these two approaches is highly desirable, especially for confocal microscopy that can exploit the advantages of both methods simultaneously. Here we show an innovative procedure of perfusion and fixation of brain tissue, that allows, by applying Golgi-Cox impregnation and immunofluorescence in the same histological section, to obtain high-quality his- tological material, with a very simple and inexpensive method. This procedure is based on three simple fixation steps: (1) a paraformaldehyde perfusion followed by a standard post-fixation to stabilize the subsequent immuno- fluorescence reaction; (2) the classical Golgi-Cox impreg- nation and (3) an immunofluorescence reaction in previously impregnated material. This combination allows simulta- neous visualization of (a) the structural details (Golgi-Cox impregnated neurons), (b) the antigens’ characterization, (c) the anatomical interactions between discrete neuronal elements and (d) the 3D reconstruction and modeling. The method is easy to perform and can be reproducibly applied by small laboratories and expanded through the use of different antibodies. Overall, the method presented in this study offers an innovative and powerful approach to study the nervous system, especially by using confocal microscopy.