A new procedure for examining Golgi impregnated neurons by light and electron microscopy

A procedure is described by which neurons impregnated by the rapid Golgi method can be de-impregnated and their fine structure studied in the electron microscope, Brains are fixed by perfusion with buffered solutions containing formaldehyde and glutaraldehyde, and pieces are then impregnated by a rapid Golgi method. Sections, 150-200 micron thick, are cut from the impregnated blocks and immersed in glycerol so that sections containing suitably impregnated neurons can be selected under the light microscope. Such sections are immersed in gold chloride followed by oxalic acid. The original impregnation deposit of silver chromate is then removed with sodium thiosulphate. This process of de-impregnation leaves the originally impregnated neurons still visible in the light microscope for they now contain a deposit of gold. In the electron microscope this deposit is apparent as fine particles that mark the profiles of the de-impregnated neurons, but the deposit is such that it does not interfere with the fine structure which is remarkably well preserved. Thus, the cytological details of the de-impregnated neurons can be discerned and their synaptic relationships can be determined.