RECENT DEVELOPMENTS IN MONOAMINE HISTOCHEMISTRY

Abstract

This chapter discusses the recent developments in the formaldehyde fluorescence technique of Falck and Hillarp to study monoamine histochemistry. With the routine procedure of the Falck–Hillarp technique, that is treatment of freeze dried tissues with formaldehyde vapors, it is extremely difficult to visualize very fine noradrenaline nerve terminals such as those present in cortical areas. Furthermore, the dopamine (DA), nerve terminals, for example, in the neostriatum do not appear as distinct dot-like fluorescent structures but as a diffuse fluorescence indicating a diffusion of the amines out of the nerve endings during the processing procedures. This technique has recently been improved6 by the introduction of glyoxylic acid, which can be used instead of formaldehyde at the perfusion and partly also at the vapour reaction step. The latter procedure is advantageous especially for the visualization of DA. Moreover, the combination of different histochemical techniques, for example, formaldehyde fluorescence with immunofluoresence, performed either on consecutive sections or on the same section, may be valuable for studying the morphological interrelationships between various neuron systems.