CONICET | Buscador de Institutos y Recursos Humanos

17beta-oestradiol is a powerful neuroprotective factor for the brain abnormalities of spontaneously hypertensive rats (SHR). 17alpha-Oestradiol, a nonfeminising isomer showing low affinity for oestrogen receptors, is also endowed with neuroprotective effects in vivo and in vitro. We therefore investigated whether treatment with 17alpha-Oestradiol prevented pathological changes of the hippocampus and hypothalamus of SHR. We used 20-week-old male SHR with a blood pressure of approximately 170 mmHg receiving s.c. a single 800 µg pellet of 17alpha-oestradiol dissolved in cholesterol or vehicle only for 2 weeks. Normotensive Wistar Kyoto (WKY) rats were used as controls. 17alpha-Oestradiol did not modify blood pressure, serum prolactin, 17beta-oestradiol levels or the weight of the testis and pituitary of SHR. In the brain, we analysed steroid effects on hippocampus Ki67+ proliferating cells, doublecortin (DCX) positive neuroblasts, glial fibrillary acidic protein (GFAP)+ astrocyte density, aromatase immunostaining and brain-derived neurotrophic factor (BDNF) mRNA. In the hypothalamus, we determined arginine vasopressin (AVP) mRNA. Treatment of SHR with 17alpha-oestradiol enhanced the number of Ki67+ in the subgranular zone and DCX+ cells in the inner granule cell layer of the dentate gyrus, increased BDNF mRNA in the CA1 region and gyrus dentatus, decreased GFAP+ astrogliosis in the CA1 subfield, and decreased hypothalamic AVP mRNA. Aromatase expression was unmodified. By contrast to SHR, normotensive WKY rats were unresponsive to 17alpha-Oestradiol. These data indicate a role for 17alpha-Oestradiol as a protective factor for the treatment of hypertensive encephalopathy. Furthermore, 17alpha-Oestradiol is weakly estrogenic in the periphery and can be used in males.