DIFFERENTIAL COLOCALIZATION OF ESTROGEN-RECEPTOR-BETA (ER-BETA) WITH OXYTOCIN AND VASOPRESSIN IN THE PARAVENTRICULAR AND SUPRAOPTIC NUCLEI OF THE FEMALE RAT-BRAIN - AN IMMUNOCYTOCHEMICAL STUDY

Evidence exists for the localization of the newly identified estrogen receptor beta (ER beta) within the rat paraventricular nucleus (PVN) a nd supraoptic nucleus (SON), regions which lack ER alpha. Presently, w e investigate whether ER beta-like-immunoreactivity (-ir) is found wit hin cells of several major neuropeptide systems of these regions. Youn g adult Sprague-Dawley rats were ovariectomized (OVX), and 1 week late r half of the animals received estradiol-17 beta (E). Dual-label immun ocytochemistry was performed on adjacent sections by using an ER beta antibody, followed by an antibody to either oxytocin (OT), arginine-va sopressin (AVP), or corticotropin releasing hormone. Nuclear ER beta-i r was identified within SON and retrochiasmatic SON, and in specific P VN subnuclei: medial parvicellular part, ventral and dorsal zones, dor sal and lateral parvicellular parts, and in the posterior magnocellula r part, medial and lateral zones. However, the ER beta-ir within magno cellular areas was noticeably less intense. OT-/ER beta-ir colocalizat ion was confirmed in neurons of the parvicellular subnuclei, in both O VX and OVX+E brains (approximate to 50% of OT and 25% of ER beta-label ed cells between bregma -1.78 and -2.00). In contrast, few PVN parvice llular neurons contained bath AVP-and ER beta-ir. As web, very little overlap aas observed in the distribution of cells containing corticotr opin releasing hormone-or ER beta-ir. In the SON, most nuclear ER beta -ir colocalized with AVP-ir, whereas few OT-/ER beta-ir dual-labeled c ells were observed. These findings suggest that estrogen can directly modulate specific OT and AVP systems through an ER beta-mediated mecha nism, in a tissue-specific manner.