A method for studying glyoxylic acid induced fluorescence and ultrastructure of monoamine neurons

Inasmuch as precise correlations of light- and electronmicroscopy are crucial for understanding biostructure, it seemed necessary to bring together the advantages of the glyoxylic acid (GA) method (for inducing monoamine fluorescence) and electron microscopy. A combined fluorescence and electron microscope method using GA is introduced. The brain is perfused by 2% GA in Krebs-Ringer bicarbonate buffer (pH 7.0) and this solution is followed by 4% paraformaldehyde containing 0.5% glutaraldehyde in Sorensen's phosphate buffer (pH 7.4). Sections are cut by cryostat or by vitratome and incubated in 2% GA in phosphate buffer (pH 7.0). Using fluorescence microscopy, features of interest are sketched and/or photographed. Afterwards, the same or subsequent section is processed for electron microscopy. Since axons of catecholamine-containing neurons (as well as their perikarya and terminals) are visualized by GA, the recommended procedure expands the range of studies concerning monoamine neurons that can now be carried out effectively.