Differential staining of catecholamines, 5-hydroxytryptamine and related compounds in aldehyde-fixed tissues

Factors influencing the fixation of biogenic amines by solutions of glutaraldehyde, formaldehyde, acrolein and glyoxal as well as the influences of these aldehydes on the histochemical reactivity of biogenic amines, have been extensively investigated. Selective stainings of 5-hydroxytryptamine, noradrenaline, dopamine and related substances in many aldehyde-fixed tissues have been achieved by systematically applying some "phenol" methods such as argentaffin, ferric-ferricyanide, diazonium and thioindoxyl reactions, and some "indole" methods such as xanthydrol, dimethylaminobenzaldehyde, vanilline, salicilaldehyde and benzaldehyde tests. The list of the structures which react like 5-hydroxytryptamine in in vitro tests includes enterochromaffin cells, carcinoid tumours, rodent mast cells, thyroid C cells, a kind of cell found in the human carotid body and chemodectomas, and some cells secreting protein hormones. NA cells of the adrenal medulla, another kind of cell in the carotid body and chemodectomas, as well as ruminants' mast cells, reacted like catecholamines in in vitro tests.