HISTOCHEMICAL DEMONSTRATION OF TRYPTAMINE. PROPERTIES OF THE FORMALDEHYDE‐INDUCED FLUOROPHORES OF TRYPTAMINE AND RELATED INDOLE COMPOUNDS IN MODELS

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Abstract
Summary: A sensitive histochemical fluorescence procedure for the demonstration of tryptamine by a formaldehyde condensation reaction has been devised. This gives a 13–18 fold increase in the fluorescence yield of tryptamine compared with the conventional Falck‐Hillarp method. The conditions of the conventional formaldehyde condensation reaction were modified in the following two ways:1. A gaseous oxidant (ozone) was introduced into the reaction vessel. Up to a certain concentration of ozone, the yield of the formaldehyde‐induced tryptamine fluorescence was markedly increased, probably because of an increased oxidative dehydrogenation of the initial condensation product. None of the other compounds tested showed such an increase in the fluorescence yield upon the combined formaldehyde‐ozone procedure. In fact, the fluorescence yields of catecholamines and 5‐HT were reduced to about 20 % compared with the yields in the conventional formaldehyde treatment. This decrease in the fluorescence intensity was presumably caused by an oxidative break‐down of the amines or of their fluorophores.2. The amine models were acidified by means of HC1‐vapour or glacial acetic acid after the conventional formaldehyde treatment, causing a marked increase in the fluorescence yield of tryptamine.The microspectrofluorimetric characteristics of the fluorophores of different indole compounds (tryptamine, N‐methyl tryptamine, 5‐HT, and tryptophan) where studied at various pH both after conventional formaldehyde treatment and after combined formaldehyde‐ozone treatment. The behaviour of the tryptamine fluorophore under various conditions was characteristic and differed from that of the other indoles and catechols tested, which makes possible the microspectrofluorimetric identification of tissue tryptamine.The combined formaldehyde‐ozone reaction and the acidification after the formaldehyde reaction have been successfully applied to tissues incubated with tryptamine, and they provide sensitive and almost selective methods for the detection of tryptamine at the cellular level.