Oxytocin increases the density of high affinity α2-adrenoceptors within the hypothalamus, the amygdala and the nucleus of the solitary tract in ovariectomized rats

Department of Molecular Medicine, Endocrine and Diabetes Unit, Karolinska Institutet/Karolinska Hospital, S-171 76 Stockholm, Sweden.
Brain Research (Impact Factor: 2.84). 08/2005; 1049(2):234-9. DOI: 10.1016/j.brainres.2005.05.034
Source: PubMed


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.

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