title: Imidazoline and alpha(2a)-adrenoceptor binding sites in postmenopausal women before and after estrogen replacement therapy.
abstract: BACKGROUND
  Platelet alpha(2A)-adrenoceptors (alpha(2A)AR) and imidazoline binding sites (subtype I(1)) have been proposed as peripheral markers of brain stem receptors that mediate sympathetic outflow and are reported to be elevated in major depression.
  
  
  METHODS
  In our study, p[(125)I]-iodoclonidine was used to assess platelet alpha(2A)AR and I(1) binding sites in healthy postmenopausal women (n = 34) compared with healthy women of reproductive age (n = 26). Receptor determinations were repeated in 19 postmenopausal women following 59-60 days of estrogen replacement therapy (ERT; 0.1 mg estradiol transdermal patches).
  
  
  RESULTS
  I(1) binding sites were twofold higher in platelets of postmenopausal women compared with women of reproduction age but were down-regulated (normalized) after 59-60 days of ERT. All other binding parameters, including platelet alpha(2A)AR density, were not different between groups nor were they changed after ERT. Platelet I(1) densities after 59-60 days of ERT were positively correlated with plasma luteinizing hormone concentrations.
  
  
  CONCLUSIONS
  It is suggested that increased imidazoline binding sites might be associated with mood and behavioral changes in postmenopausal women.
authors.affiliation: Department of Psychiatry and Human Behavior, and Departments of Pharmacology and Physiology, University of Mississippi Medical Center, Jackson, Mississippi, USA.
authors.forename: J E
authors.initials: JE
authors.lastname: Piletz
authors.forename: U
authors.initials: U
authors.lastname: Halbreich
mesh_terms: D000328:Adult; D000345:Affinity Labels; D001665:Binding Sites; D001792:Blood Platelets / Q000737:chemistry / Q000378:metabolism; D003000:Clonidine / Q000031:analogs & derivatives; D003866:Depressive Disorder / Q000378:metabolism; D015536:Down-Regulation / Q000187:drug effects; D015914:Estrogen Replacement Therapy; D005260:Female; D006801:Humans; D054755:Imidazoline Receptors; D007457:Iodine Radioisotopes; D007986:Luteinizing Hormone / Q000378:metabolism; D008593:Menopause / Q000378:metabolism; D008875:Middle Aged; D017698:Postmenopause / Q000378:metabolism*; D011869:Radioligand Assay; D018341:Receptors, Adrenergic, alpha-2 / Q000096:biosynthesis / Q000378:metabolism*; D011955:Receptors, Drug / Q000096:biosynthesis / Q000378:metabolism*
chemical_list: D000345:Affinity Labels; D054755:Imidazoline Receptors; D007457:Iodine Radioisotopes; D018341:Receptors, Adrenergic, alpha-2; D011955:Receptors, Drug; C053113:4-iodoclonidine; D007986:Luteinizing Hormone; D003000:Clonidine