Ultrastructural changes in hypothalamic supraoptic nucleus neurons of ovariectomized estrogen-deprived young rats

We report the occurrence of neuronal degeneration in the supraoptic nucleus of the hypothalamus of prepubertal female rats as a consequence of ovariectomy followed by estrogen deprivation (OVX-EB). In contrast, no degenerating neurons were observed in ovariectomized rats treated with estrogens (OVX + EB) or sham-operated animals. The altered neurons in the OVX-EB group presented a cytoplasm with dilation of the rough endoplasmic reticulum lumen. The nuclear envelope also appeared dilated. There was mitochondrial swelling with disintegrated cristae, while lysosomes appeared intact. The cell nucleus showed a pattern of chromatin condensation and a nucleolus hardly distinguishable from the nucleoplasm. The neuronal alterations reported here may be due to altered gene expression in the cell nucleus resulting from induced hormonal loss during early postnatal development.