Author(s): Petersson M, Lundeberg T, UvnsMoberg K
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Abstract To investigate how the effects of oxytocin on blood pressure are influenced by female sex hormones, oxytocin (1 mg/kg, s.c.) was given to intact cycling and ovariectomized (OVX) female rats. Oxytocin caused a transient increase in blood pressure, most pronounced during proestrus (p < 0.01) and estrus (p < 0.01). This increase was partially antagonized by an oxytocin antagonist. When oxytocin was given for 5 days, blood pressure decreased (intact rats: 123+/-1.5 vs. 130+/-1.3 mm Hg; p < 0.001, OVX rats: 120+/-3.0 vs. 129+/-1.1 mm Hg; p < 0.001). This decrease, not abolished by the oxytocin antagonist, persisted for 3 weeks in intact rats and for 8 days in OVX rats. If oxytocin treatment of OVX rats continued, a nadir of 12 mm Hg (118+/-1.7 mm Hg; p < 0.001) was reached after 8 days. Thereafter heart rate decreased significantly (p < 0.05). One daily oxytocin injection for 12 days to OVX rats decreased blood pressure for 3 weeks, as in intact rats. These results show that acute and chronic oxytocin treatment cause opposite effects on blood pressure, and that these effects are modified by female sex hormones.
This article was published in J Cardiovasc Pharmacol
and referenced in Journal of Autacoids and Hormones