On the method of glenner for the histochemical demonstration of the monoamine oxidase (MAO)

Summary The method of Glenner et al. for the histochemical demonstration of MAO activity was studied by means of scanning microdensitometry and discrete measurement of optical density (-590 nm) of the liver and brain tissues sections.The experiments indicated that: (1) The optimal time of incubation (the thickness of sections is 15 m) is 60–90 min. (2) The histochemical reaction proceeds with the following substrates: dopamine, noradrenalin, serotonin, and tryptamine. (3) Iproniazid is the best inhibitor for preincubation whereas for simultaneous inhibition the substrate semicarbazide is better. (4) The incubation under the anaerobic conditions caused a considerable decrease of the stain intensity of the sections. We consider these data to indicate that both the aldehydes and acids formed under oxidation may take part in direct reduction of NBT to diformazan. (5) The histochemical reaction for MAO without substrates testifies to the presence of endogenous amines or other redox reactions leading to the reduction of NBT.