Abstract
The effects of 17 β-estradiol and progesterone on MAO activity in seven regions of the brain and in their target organ, the endometrium, were examined. In intact animals in diestus, (confirmed by vaginal smears), MAO activity in various regions of the brain decreased in the following order : hypothalamus>hippocampus>cortex≅striatum>cerebellum≅midbrain>medulla oblongata. The activity in the medulla oblongata was about half that in the hypothalamus. In ovariectomized rats 14 days after operation the activities in the various regions of the brain were not significantly different from those in normal rats. The MAO activity in the endometrium was 2.6 times higher in ovariectomized rats than in intact animals. Injection of 17 β-estradiol for three consecutive days decreased MAO activity in the brain, the decrease being greater in ovariectomized rats. The decrease was greatest (13-15%) in the cortex of intact rats and the cerebellum, hypothalamus and cortex of ovariectomized rats. Injection of progesterone (4 mg/kg) for three consecutive days cause a significant increase in MAO activity in the cortex of intact rats ; injection of progestrone (2 mg or 4 mg/kg) for three consecutive days caused a slight, but not significant, increase in MAO activity in the hypothalamus and medulla oblongata. Injection of 19-norethisterone (0.4 mg/kg) for three consecutive days caused a slight increase in MAO activity in the hypothalamus only. A single injection of 17 β-estradiol (0.2 mg/kg) increased MAO activity significantly in the midbrain after two hours, but did not affect the activity in other areas. A single injection of progesterone (4 mg/kg) caused no changes in MAO activity. Injection of 17 β-estradiol (0.2 mg/kg) for three consecutive days decreased MAO activity significantly in the endometrium, especially in ovariectomized rats. Progesterone increased endometrium MAO activity significantly in intact rats, but not in ovariectomized rats. No significant differences were observed in the weight or protien content of the brain of intact or ovariectomized rats after repeated injections of 17 β-estradiol (0.2 mg/kg, s.c.), progesterone (2 mg or 4 mg/kg, s.c.) or 19-norethisterone (0.4 mg/kg, s.c.) ora single injection of 17 β-estradiol (0.2 mg/kg, i.p.) or progesterone (4 mg/kg, i.p.) compared with the values of the controls. Injection of 17 β-estradiol (0.2 mg/kg) for three consecutive days caused a significant increase in tissue weight of the endometrium of ovariectomized rats. It also increased the uterine weight of intact rats and the protein content of intact and ovariectomized rats, but the changes from the control values were not statistically significant. Repeated injects of progestrone did not affect the uterine weight or the protein content of intact or ovariectomized rats.
