Monoamine oxidase in the neurohypophysis of the newt (Cynops pyrrhogaster pyrrhogaster), the toad (Bufo bufo japonicus) and the tortoise (Clemmys japonica)

Quantitative aspects of the histochemical tetrazolium salt reaction on monoamine oxidase activity in rat liver

The tetrazolium method for the histochemical detection of monoamine oxidase (MAO) activity in rat liver cryostat sections has been tested for its specificity and its possible use in quantification. The tetrazolium salt tetranitro blue tetrazolium is recommended for the localization of MAO activity, rather than nitro blue tetrazolium or BPST [2-(2-benzothiazolyl)-3-(4-phthalhydrazidyl)-5-styryl-tetrazolium] . Hardly any formazan was produced in the absence of the substrate tryptamine and Marsilid, a specific inhibitor of MAO activity, prevented formazan production almost completely. A linear relationship between the integrated absorbance measured with a microdensitometer and either the incubation period or section thickness was obtained. We conclude that the method described in this paper can be used for the quantitative analysis of MAO activity in tissue sections of rat liver. MAO activity was found to be 20-25% higher in the periportal zone of rat liver than in the perivenous zone.

Distribution of monoamine oxidase (MAO) in relation to the hypothalamo-hypophyseal system of the teleost Clarias batrachus (L.)

Varying degrees of monoamine oxidase (MAO) activity were noticed all along the hypothalamo-hypophyseal neurosecretory tract in C. batrachus. Intense activity was evident on the wall of the secretory cells of the adenohypophysis, neurons of the nucleus preopticus (NPO) and nucleus lateralis tuberis (NLT). However, MAO activity was also observed in the cytoplasm of some neurons in the ventromedian region of the NLT and groups of cells present in the neurohypophyseal ramifications of the pars intermedia. A strong accumulation of formazan granules in the median eminence (ME) and the neuroadeno interface lends further support to the view that C. batrachus has a ME of both the tetrapodan and the teleostean type. The distributional pattern of MAO in the hypothalamus and hypophysis suggests that monoaminergic fibres are probably involved in the secretory mechanism of the releasing factors and pituitary hormones.