Short-term increase and long-term decrease of blood pressure in response to oxytocin-potentiating effect of female steroid hormones.
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.
Petersson
M
M
Department of Molecular Medicine, Karolinska Hospital, Stockholm, Sweden.
Lundeberg
T
T
Uvnäs-Moberg
K
K
D000704:Analysis of Variance; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects*; D004357:Drug Synergism; D004971:Estrus; D005260:Female; D012739:Gonadal Steroid Hormones / Q000502:physiology*; D006339:Heart Rate / Q000187:drug effects*; D010052:Ovariectomy; D010121:Oxytocin / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley
D012739:Gonadal Steroid Hormones; D010121:Oxytocin