title: Estrogen receptor-alpha expression in osmosensitive elements of the lamina terminalis: regulation by hypertonicity.
abstract: The subfornical organ (SFO), median preoptic nucleus (MnPO), and organum vasculosum lamina terminalis (OVLT), which are associated with the lamina terminalis, are important in the control of body fluid balance. Neurons in these regions express estrogen receptor (ER)-alpha, but whether the ER-alpha neurons are activated by hypertonicity and whether hypertonicity regulates ER-alpha expression are not known. Using fluorescent, double-label immunocytochemistry, we examined the expression of ER-alpha-immunoreactivity (ir) and Fos-ir in control and water-deprived male rats. In control animals, numerous ER-alpha-positive neurons were expressed in the periphery of the SFO, in both the dorsal and ventral MnPO, and in the dorsal cap of the OVLT. Fos-positive neurons were sparse in euhydrated rats but were numerous in the SFO, MnPO, and the dorsal cap of the OVLT after 48-h water deprivation. Most ER-alpha-ir neurons in these areas were positive for Fos, indicating a significant degree of colocalization. To examine the effect of dehydration on ER-alpha expression, animals with and without lesions surrounding the anterior and ventral portion of the 3rd ventricle (AV3V) were water deprived for 48 h. Water deprivation resulted in a moderate increase in ER-alpha-ir in the SFO of sham-lesioned rats (P = 0.03) and a dramatic elevation in AV3V-lesioned animals (P < 0.05). This was probably induced by the significant increase in plasma osmolality in both dehydrated groups (P < 0.001) rather than a decrease in blood volume, because hematocrit was significantly increased only in the dehydrated sham-lesioned animals. Thus these studies implicate the osmosensitive regions of the lamina terminalis as possible targets for sex steroid effects on body fluid homeostasis.
authors.affiliation: Department of Physiology and Biophysics, University of Colorado Health Science Center, 4200 E. Ninth Ave. Box C240, Denver, CO 80262, USA.
authors.forename: Suwit J
authors.initials: SJ
authors.lastname: Somponpun
authors.forename: Alan Kim
authors.initials: AK
authors.lastname: Johnson
authors.forename: Terry
authors.initials: T
authors.lastname: Beltz
authors.forename: Celia D
authors.initials: CD
authors.lastname: Sladek
mesh_terms: D000818:Animals; D003681:Dehydration / Q000378:metabolism; D047628:Estrogen Receptor alpha; D007031:Hypothalamus / Q000378:metabolism*; D007150:Immunohistochemistry; D008297:Male; D009474:Neurons / Q000378:metabolism; D011301:Preoptic Area / Q000378:metabolism; D016760:Proto-Oncogene Proteins c-fos / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D011960:Receptors, Estrogen / Q000378:metabolism*; D013356:Subfornical Organ / Q000378:metabolism; D020542:Third Ventricle / Q000378:metabolism; D013997:Time Factors; D014018:Tissue Distribution; D014868:Water Deprivation / Q000502:physiology*
chemical_list: D047628:Estrogen Receptor alpha; D016760:Proto-Oncogene Proteins c-fos; D011960:Receptors, Estrogen