IMPROVED HISTOFLUORESCENCE PROCEDURE FOR FREEZE-DRIED PARAFFIN-EMBEDDED TISSUE BASED ON COMBINED FORMALDEHYDE-GLYOXYLIC ACID PERFUSION WITH HIGH MAGNESIUM CONTENT AND ACID PH

A technique is described for highly sensitive and precise visualization of central catecholamine systems in paraffin sections of freeze-dried tissue. The procedure is based on perfusion of the animal with a solution containing formaldehyde and/or glyoxylic acid, in the presence of a very high Mg content (40 g MgSO4/150 ml solution) and acid pH. The perfused tissue is rapidly frozen, freeze-dried, treated with formaldehyde vapors (at +80.degree. C for 1 h), embedded in paraffin in vacuo and finally sectioned. The technique has a sensitivity for the dopamine- and noradrenaline-containing systems that is comparable with that of the glyoxylic acid-Vibratome technique, which utilizes fresh, glyoxylic acid-perfused tissue. The preterminal axon pathways become fluorescent throughout their full extent and the several new terminal systems, discovered with the glyoxylic acid-Vibratome method, are well demonstrable. The method is also highly useful for the study of the cell bodies and their dendritic processes. The catecholamine fiber systems are visualized without any signs of diffusion and with a richness in detail. In animals pretreated with L-tryptophan and MAO-inhibitor the technique is also useful for studies on central indolamine-containing systems. [Rats were used in this study.].