Imidazoline and α2A-adrenoceptor binding sites in postmenopausal women before and after estrogen replacement therapy

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[I-125]-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. (C) 2000 Society of Biological Psychiatry.