Estradiol treatment decreases type A and increases type B monoamine oxidase in specific brain stem areas and cerebellum of ovariectomized rats.

Ovariectomized rats were given either acute (50 micrograms 12 h or 24 h before sacrifice) or chronic (2 micrograms/day for one month) subcutaneous administration of 17 beta-estradiol. The activities of both type A and type B monoamine oxidase (MAO) in the cerebellum and in the areas A1, A2, and locus coeruleus of the brain stem were determined. The activity of type B MAO was increased by acute and chronic estrogen treatment in the different areas studied, whereas that of type A MAO did not change in the areas A1 and A2 and was decreased in the locus coeruleus and the cerebellum. These results indicate a discriminative action of estrogens on different forms of monoamine oxidase.