Article

Oxytocinergic activity is linked to lower blood pressure and vascular resistance during stress in postmenopausal women on estrogen replacement.

School of Medicine, University of North Carolina at Chapel Hill, NC 27599-7175, USA.
Hormones and Behavior (impact factor: 3.87). 06/2005; 47(5):540-8. DOI:10.1016/j.yhbeh.2004.12.010 pp.540-8
Source: PubMed

ABSTRACT Estrogen administration results in increased release of the oxytocin (OT) prohormone reflected by increases in oxytocin intermediate peptide (OT Int) in both animal models and humans, and sequential treatment of ovariectomized rats with estrogen/progesterone then progesterone withdrawal leads to increased hypothalamic OT mRNA. Blood pressure (BP) reductions have been related to increased exogenous and endogenous OT in rats and to higher endogenous OT activity in premenopausal women, but not previously in postmenopausal women. Thus, we used plasma obtained at rest and during a speech stressor from 54 postmenopausal women who participated in a 6-month randomized trial of oral conjugated estrogens vs. placebo to examine effects of estrogen replacement therapy (ERT) on plasma OT and OT Int levels and their relationships to changes in BP during the trial. ERT alone and with progesterone (but not placebo) led to significant increases in plasma levels of OT Int, but no change in plasma OT levels. Women showing greater increases in OT Int during treatment showed greater decreases in BP and total vascular resistance during a series of behavioral stressors compared to women with moderate or no increases in OT Int, even after controlling for effects related to treatment condition or to changes in plasma estradiol. The findings suggest that enhanced oxytocinergic activity may contribute to BP decreases associated with ERT in more responsive postmenopausal women.

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Keywords

54 postmenopausal women
 
6-month randomized trial
 
BP decreases
 
endogenous OT
 
Estrogen administration results
 
estrogen replacement therapy
 
estrogen/progesterone
 
greater decreases
 
greater increases
 
higher endogenous OT activity
 
oral conjugated estrogens
 
OT Int levels
 
ovariectomized rats
 
plasma estradiol
 
plasma levels
 
plasma OT
 
plasma OT levels
 
sequential treatment
 
significant increases
 
total vascular resistance