Estradiol target neurons in the hypothalamic arcuate nucleus and lateral ventromedial nucleus of young adult, reproductively senescent, and monosodium glutamate-lesioned female golden hamsters.

Histoautoradiographic methods were used to assess estrogen target neurons in the hypothalamic arcuate nucleus (ARC) and ventromedial nucleus, lateral portion (LVM), comparing young adult and aged female golden hamsters. A subgroup of young adult females had ARC lesions induced by monosodium glutamate at neonatal day 8. All were ovariectomized to remove endogenous estrogens. Controls were given nonradioactive estradiol. After 3H-estradiol (3H-E2) was injected intravenously, hypothalami were removed, frozen, and processed for histoautoradiography. In the ARC and LVM the ratio of 3H-E2 labelled neurons to total neurons counted was significantly lower in the older animals. Young females with ARC lesions had very few 3H-E2 labelled neurons remaining in the ARC but had a normal complement in the LVM. Although 3H-E2 labelled ARC neurons were notably decreased in old females, those ARC neurons that were labelled in the old had virtually the same frequency distribution of the labelling index as in the young, suggesting no change in the average estrogen uptake per target cell.

Uterine progesterone receptors in the aged golden hamster.

Uterine capacity to form cytoplasmic progesterone receptor was compared in ovariectomized golden hamsters at three months and 15-17 months of age. A dose-response test with 17beta-estradiol(E2) showed that the uterine content of progesterone receptor (pmole/uterus) was equal in young and old at all dose levels. However, heavier old uteri had less receptor per gm tissue. Old and young hamsters were mated, ovariectomized on day 7 post coitum and after two weeks, all were given the same dose of E2. Endometrium was separated from myometrium before analysis of progesterone receptor. Myometrium was analyzed for both estrogen and progesterone receptors. Myometrium of both groups had comparable levels of both receptors. The mean concentration of progresterone receptor (pmole/gm tissue) was higher in old endometrium. Some old animals with liver, kidney and adrenal disease had more endometrial reaction after E2 treatment. A few with low endometrial receptor levels had normal livers but at least one sterile uterine horn. There was, however, no general decline with age in intrinsic uterine capacity to form progesterone receptors.