Hypotalamic monoamine oxidase activity in ovariectomized rats after sexual behavior restoration

The effect of estradiol benzoate, progesterone and a sequential treatment with both on the activity of the enzyme monoamine-oxidase (MAO) was assessed in mitochondria from hypothalami of ovariectomized rats. A differential effect on the subtypes A and B MAO was found according to the type of treatment. Estradiol benzoate administration decreases MAO activity, mainly that of MAO-A. Progesterone alone had no effect, and sequential treatment with estradiol benzoate plus progesterone restored sexual behavior and produced a significant increase of MAO-A activity, whitout changes in total MAO activity. Since MAO-A is an isoform of MAO that preferentially uses norepinephrine and serotonin as substrates and MAO-B acts on phenylethylamine and benzylamine as substrates, our findings suggest that the restoration of sexual behabior after the treatment with estradiol benzoate followed by progesterone may be associated with the differential effect exerted by the hormones on MAO subtypes, rather than to the simple decrease in hypothalamic monoamine concentrations as reported in the literature

Antiestrogen U23,469 induced alterations of catecholamine levels on plasma and central nervous system

The effect of antiestrogen U23,469 administration in vivo on the centration of dopamine, norepinephrine and epinephrine in the plasma, cerebral cortex and hypothalamus in ovariectomized rats was investigated. Rats were treated with estradiol benzoate, progesterone and U23,469 in different doses, s.c., daily for 6 days. Control group was injected with sesame oil. Catecholamines were estimated by radioenzymatic assay. Six days of U23,469, estradiol benzoate, progesterone or its combination altered the catecholamine levels compared to the control. Dopamine decreased in plasma with progesterone and U23.469. In the cerebral cortex, progesterone and U23,469 increased significantly and in the hypothalamus all the treatments produced a decrease of catecholamines. The levels of NE were reduced with estradiol benzoate, progesterone and U23,469; there was no significant difference in the norepinephrine levels after different treatments in the cerebral cortex, but the NE levels were significantly decreased inthe hypothalamus. Epinephrine Showed differences related to the treatment, as in plasma, as in cerebral cortex and hypothalamus. These resultas suggest that antiestrogen treatment compared with the estradiol benzoate or progesterone may affect the catecholamine levels of the central nervous system and plasma and support the idea that AE could have an indirect effect on the catecholaminergic system