Microspectrofluorometric characterization of the fluorescent derivatives of biogenic amines produced by aqueous aldehyde (Faglu) fixation.

The fluorescent derivatives of the reaction between an aqueous aldehyde (Faglu) solution and the biogenic amines (5-hydroxytryptamine, dopamine and noradrenaline) have been examined in the order to determine the conditions required for maximal fluorescence yield. The fluorescence intensity and spectra of the final reaction products have been characterized and found to be highly dependent on the pH of the reaction mixture, Fluorophores derived from catecholamines have maximal yield and are most easily characterized when the reaction is performed at pH 7.3, whilst those derived from 5-hydroxytryptamine have maximal yield and are most readily characterized when the reaction is performed at pH 10.0. The addition of potassium ferricyanide to the Faglu further enhances the fluorescence yield of 5-hydroxytryptamine-containing models and tissues at both pH 10.0 and pH 7.3. Using the modified Faglu reaction mixture, it has been possible to demonstrate 5-hydroxytryptamine in the central nervous system without the need for pharmacological manipulation.