Chronic estradiol treatment increases ovariectomized rat striatal D-1 dopamine receptors.
Striatal D-1 dopamine (DA) receptors were investigated following chronic 17 beta-estradiol (10 micrograms, b.i.d., s.c., for two weeks) to ovariectomized (OVX) female rats. This treatment initiated the day after ovariectomy has revealed that the maximal density in homogenates of striatal D-1 DA receptors (Bmax) labelled with [3H] SCH 23390 was increased (44% without and 28% with 120 mM NaCl in the assay buffer). Estradiol treatments initiated 2 or 4 weeks after ovariectomy did not induce D-1 DA receptor binding modifications. The affinity (Kd) of the ligand for the receptor remains unchanged by the steroid treatment while NaCl increased both the density and the affinity of [3H] SCH 23390 binding to striatal D-1 DA receptors. By autoradiography, the increase of striatal [3H] SCH 23390 binding to D-1 DA receptors after chronic estradiol treatment was found to be homogenously distributed in this brain region. Thus, chronic treatment with estradiol of ovariectomized rats leads to an increased density of striatal D-1 DA receptors but, this hormonal modulation of D-1 DA receptors is lost when treatment is started 2 weeks after ovariectomy or later.
Lévesque
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School of Pharmacy, Laval University, Québec, Canada.
Di Paolo
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D000818:Animals; D001552:Benzazepines / Q000378:metabolism; D003342:Corpus Striatum / Q000187:drug effects / Q000378:metabolism*; D018492:Dopamine Antagonists; D004958:Estradiol / Q000008:administration & dosage / Q000494:pharmacology*; D005260:Female; D010052:Ovariectomy; D051381:Rats; D011919:Rats, Inbred Strains; D011954:Receptors, Dopamine / Q000378:metabolism*; D017447:Receptors, Dopamine D1
D001552:Benzazepines; D018492:Dopamine Antagonists; D011954:Receptors, Dopamine; D017447:Receptors, Dopamine D1; D004958:Estradiol