Oxytocin increases the density of high affinity alpha(2)-adrenoceptors within the hypothalamus, the amygdala and the nucleus of the solitary tract in ovariectomized rats.
Oxytocin induces long-term changes in, for example, blood pressure, spontaneous motor activity and corticosterone levels in rats. Previous studies in male rats have suggested a role for alpha(2)-adrenoceptors within the central nervous system in these effects. The aim of the present study was to investigate if oxytocin treatment in female rats would influence alpha(2)-adrenoceptors within the hypothalamus, the amygdala and the nucleus of the solitary tract (NTS). For this purpose, female ovariectomized (OVX) rats were treated with oxytocin (1 mg/kg s.c.) or saline once a day for 10 days. Rats were decapitated 5 days after the last injection, and brains and plasma were collected. Quantitative receptor autoradiography for characterization of high affinity alpha(2)-adrenoceptor agonist binding and radioimmunoassay for corticosterone were performed. Oxytocin increased the B(max) values of the alpha(2)-adrenoceptor agonist [3H]UK14.304 binding sites significantly in all the analyzed areas (P<0.05). K(d) values were unchanged. Plasma levels of corticosterone were significantly decreased in the oxytocin-treated rats (P<0.05). These findings are in further support of an interaction between oxytocin receptors and alpha(2)-adrenoceptors and show that oxytocin treatment may increase alpha(2)-adrenoceptor recognition probably leading to an increase in alpha(2)-adrenoceptor signaling in several parts of the brain.
Petersson
Maria
M
Department of Molecular Medicine, Endocrine and Diabetes Unit, Karolinska Institutet/Karolinska Hospital, S-171 76 Stockholm, Sweden. maria.peterson@molmrd.ki.se
Diaz-Cabiale
Zaida
Z
Angel Narváez
José
J
Fuxe
Kjell
K
Uvnäs-Moberg
Kerstin
K
D000316:Adrenergic alpha-Agonists / Q000493:pharmacokinetics; D000679:Amygdala / Q000187:drug effects*; D000818:Animals; D001345:Autoradiography / Q000379:methods; D001665:Binding Sites / Q000187:drug effects; D000068438:Brimonidine Tartrate; D004305:Dose-Response Relationship, Drug; D005260:Female; D007031:Hypothalamus / Q000187:drug effects*; D010052:Ovariectomy / Q000379:methods; D010121:Oxytocin / Q000494:pharmacology*; D011810:Quinoxalines / Q000493:pharmacokinetics; D011863:Radioimmunoassay / Q000379:methods; D051381:Rats; D017207:Rats, Sprague-Dawley; D018341:Receptors, Adrenergic, alpha-2 / Q000378:metabolism*; D017552:Solitary Nucleus / Q000187:drug effects*; D014316:Tritium / Q000493:pharmacokinetics
D000316:Adrenergic alpha-Agonists; D011810:Quinoxalines; D018341:Receptors, Adrenergic, alpha-2; D014316:Tritium; D000068438:Brimonidine Tartrate; D010121:Oxytocin