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Histochemical demonstration of monoamine oxidase‐containing neurons and an age‐related increase of the enzyme activity in the mouse brain
Author(s) -
Yoshimura Noriaki,
Sato Tsuyoshi,
Nishimura Masahiko,
Tohyama Chiharu
Publication year - 1998
Publication title -
neuropathology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.701
H-Index - 61
eISSN - 1440-1789
pISSN - 0919-6544
DOI - 10.1111/j.1440-1789.1998.tb00076.x
Subject(s) - locus coeruleus , monoamine oxidase , monoamine neurotransmitter , nucleus , serotonin , monoamine oxidase a , brainstem , chemistry , pons , endocrinology , biology , medicine , neuroscience , enzyme , biochemistry , receptor
Monoamine‐containing neurons are especially rich in monoamine oxidase (MAO) and are clustered mainly within the brainstem and diencephalon. They are known to be affected in neurodegenerative disorders such as Parkinson's and Alzheimer's diseases. To investigate the distribution of MAO‐containing neurons and any changes in MAO activity with age, brains of male mice (C3H strain) in various age groups ( n = 3–5) were studied histochemically and biochemically. Histochemical measurement of MAO activity (the coupled peroxidation method) clearly visualized the localization of MAO‐containing neurons in the mouse brain, such as locus coeruleus, nucleus centralis superior, nucleus raphe dorsalis, etcetera. The staining intensity (MAO activity) of these neurons, within both somata and neurites, increased with age and was accompanied by a moderate increase in neuropils. The biochemical assay (Kraml's method) revealed an age‐related increase in MAO activity, with an abrupt rise until 3 months of age, followed by a further gradual rise until 32 months of age, the age limit examined. To devise a method that is easily applicable to human tissues, the original histochemical method was modified; perfusion fixation was replaced by immersion fixation of sections for 1 min. The result was almost as good as that obtained by the original method. By this modified method, unfixed brains after decapitation of adult mice were kept at 4°C or −20°C for various time intervals and sequentially observed. The observations demonstrated that when brains were frozen immediately after killing and stored at −20°C for 24 h or longer, or cooled and stored at 4°C for 6 h or less, all proved to be suitable for morphological analysis of changes in MAO‐containing neurons. Therefore, this modified method should be applicable to human materials in such diseases as described above.