The development of connections of the magnocellular hypothalamic nuclei with the posterior hypophyseal lobe in rat prenatal ontogeny]

The development of projections of the hypothalamic nuclei into the posterior lobe of the pituitary was studied on the fixed brain of rat fetuses from day 15 until day 19 of embryogenesis using retrograde staining with the fluorescent carbocyanine dye DiI. The formation of connections of the supraoptic and retrochiasmatic nuclei of the hypothalamus with the posterior lobe of the pituitary takes place during prenatal development on days 15 and 16-17, respectively, while only an insignificant number of the paraventricular nucleus neurons send their axons to the posterior lobe of the pituitary in rat fetuses. These facts suggest different temporal involvement of the above nuclei in formation of the hypothalamic-hypophysial neurosecretory system in rat fetuses.