Estrogen receptor alpha is involved in the estrogenic regulation of arginine vasopressin immunoreactivity in the supraoptic and paraventricular nuclei of ovariectomized rats

The ovarian hormone estradiol regulates the expression of arginine vasopressin gene and the release of arginine vasopressin by magnocellular hypothalamic neurons. Magnocellular neurons express estrogen receptor β and are contacted by afferent neurons that express estrogen receptor α. In this study we have assessed the effect of selective ligands for estrogen receptors to determine the subtype of estrogen receptor involved in the regulation of arginine vasopressin immunoreactivity in the supraoptic and paraventricular nuclei of ovariectomized rats. The volume fraction occupied by arginine vasopressin immunoreactive material was significantly increased in both nuclei in the animals treated with estradiol compared to the animals injected with vehicle. A similar result was obtained with an estrogen receptor α selective agonist. In contrast, the administration of an estrogen receptor β selective agonist did not significantly affect arginine vasopressin immunoreactivity. This finding suggests that estradiol may regulate arginine vasopressin levels on the supraoptic and paraventricular nuclei by acting on afferent neurons expressing estrogen receptor α.