Autoradiographic localization of estradiol- and progesterone-concentrating neurons in the isolated rhesus monkey hypothalamus.

Progesterone- and estradiol-concentrating neurons were autoradiographically localized in the in situ, vascularly isolated, rhesus monkey hypothalamus. Estradiol-concentrating neurons were dispersed throughout the hypothalamus, their density being greatest in the medial preoptic (MPOA) and medial basal hypothalamic nuclei (viz. dorsomedial, ventromedial (VMH) and infundibular nuclei). In contrast, progesterone-concentrating neurons were less densely localized in the medial preoptic, ventromedial (medial division) and infundibular nuclei. There was a virtual absence of progestin-concentrating cells in the anterior and posterior hypothalamic zones. This localization of cells was not attributed to the perfusion pattern of the isolated hypothalamus since a complete distribution of injected microspheres was found throughout the hypothalamus. The results of these studies indicate that a possible division between estradiol- and progesterone-concentrating neurons exists within the MPOA-medial basal hypothalamic nuclei of the rhesus monkey.