Co-localization of estrogen and angiotensin receptors within subfornical organ neurons

A double-staining immunocytochemical study was done in ovariectomized (OVX) female rats that were either treated with 17 beta-estradiol (E-2) (OVX + E -2,) to produce an approximate circulating level of 30 pg/ml plasma, or not -treated with E-2, (OVX), to investigate the distribution of subfornical or gan (SFO) neurons that contained estrogen receptors (ER), and to determine whether these neurons also contained the angiotensin AT(I)R-receptor (AT(I) R). Neurons that contained either ER-like immunoreactivity only, AT,R-like immunoreactivity only, or both ER and AT,R immunoreactivity were found thro ughout the extent of the SFO in both the OVX + E-2:, and OVX rats. However, some regional differences were apparent in both groups of female rats. Neu rons containing the ER were predominantly found in the peripheral regions o f the SFO, near large blood vessels and the ependymal layer of the third ve ntricle. A number of lightly stained ER containing neurons was also observe d scattered throughout the central core region of the SFO. (OVX) only anima ls were found to have a larger number of ER containing neurons in the SFO c ompared to the E-2, treated animals. Neurons containing AT,R were also foun d throughout the SFO, but without a distinct distribution pattern in either group of rats, although there were more neurons that exhibited AT(I)R immu noreactivity in the OVX animals. Finally, a distinct group of SFO neurons w as found that exhibited both ER and AT,R immunoreactivity in both groups of animals, although a larger number of these double labelled neurons was fou nd in the OVX animal. Most of these neurons were also found along the perip heral border of the SFO in close proximity to blood vessels and the Ventric ular lining. These data have demonstrated the co-existence of ER and AT,R i n SFO neurons of the female rat, and suggest that circulating level of E-2, alter the expression of both the ER and AT(I)R in these neurons. In additi on, these data suggest that E-2, may alter the physiological responses of S FO neurons to angiotensin II by down regulating the number of AT,R. (C) 199 9 Elsevier Science B.V. All rights reserved.