Nucleus in the anterior part of the hypothalamus. (MSH) * one of the magnocellular hypothalamic nuclei, an elongated plate of large, deeply staining cells located close to the third ventricle in the anterior hypothalamic area; major source of oxytocin and to a lesser extent, of antidiuretic hormone, neurohormones, which are carried to the neurohypophysis along the paraventriculohypophysial tract. (CSP). [ ]