title: Greater Beta-Adrenergic Receptor Mediated Vasodilation in Women Using Oral Contraceptives.
abstract: BACKGROUND
  β-adrenergic receptors play an important role in mitigating the pressor effects of sympathetic nervous system activity in young women. Based on recent data showing oral contraceptive use in women abolishes the relationship between muscle sympathetic nervous system activity and blood pressure, we hypothesized forearm blood flow responses to a β-adrenergic receptor agonist would be greater in young women currently using oral contraceptives (OC+, n = 13) when compared to those not using oral contraceptives (OC-, n = 10).
  
  
  METHODS
  Women (18-35 years) were studied during the early follicular phase of the menstrual cycle (days 1-5) or placebo phase of oral contraceptive use. Forearm blood flow (FBF, Doppler ultrasound) and mean arterial blood pressure (MAP, brachial arterial catheter) were measured at baseline and during graded brachial artery infusion of the β-adrenergic receptor agonist, Isoproterenol (ISO), as well as Acetylcholine (ACH, endothelium-dependent vasodilation) and Nitroprusside (NTP, endothelium-independent vasodilation). Forearm vascular conductance was calculated (FVC = FBF/MAP, ml/min/100 mmHg) and the rise in FVC from baseline during infusion quantified vasodilation (ΔFVC = FVCinfusion - FVCbaseline).
  
  
  RESULTS
  ISO increased FVC in both groups (p < 0.01) and ISO-mediated ΔFVC was greater in OC+ compared to OC- (Main effect of group, p = 0.02). Expressing data as FVC and FBF resulted in similar conclusions. FVC responses to both ACH and NTP were also greater in OC+ compared to OC-.
  
  
  CONCLUSIONS
  These data are the first to demonstrate greater β-adrenergic receptor-mediated vasodilation in the forearm of women currently using oral contraceptives (placebo phase) when compared to those not using oral contraceptives (early follicular phase), and suggest oral contraceptive use influences neurovascular control.
authors.affiliation: Department of Kinesiology, University of Wisconsin Madison, WI, USA.
authors.forename: Jacqueline K
authors.initials: JK
authors.lastname: Limberg
authors.affiliation: Department of Kinesiology, University of Wisconsin Madison, WI, USA.
authors.forename: Garrett L
authors.initials: GL
authors.lastname: Peltonen
authors.affiliation: Department of Kinesiology, University of Wisconsin Madison, WI, USA.
authors.forename: Rebecca E
authors.initials: RE
authors.lastname: Johansson
authors.affiliation: Department of Kinesiology, University of Wisconsin Madison, WI, USA.
authors.forename: John W
authors.initials: JW
authors.lastname: Harrell
authors.affiliation: Department of Kinesiology, University of Wisconsin Madison, WI, USA.
authors.forename: Jeremy M
authors.initials: JM
authors.lastname: Kellawan
authors.affiliation: Department of Kinesiology, University of WisconsinMadison, WI, USA; Department of Pediatrics, University of WisconsinMadison, WI, USA.
authors.forename: Marlowe W
authors.initials: MW
authors.lastname: Eldridge
authors.affiliation: Department of Anesthesiology, University of Wisconsin Madison, WI, USA.
authors.forename: Joshua J
authors.initials: JJ
authors.lastname: Sebranek
authors.affiliation: Department of Anesthesiology, University of Wisconsin Madison, WI, USA.
authors.forename: Benjamin J
authors.initials: BJ
authors.lastname: Walker
authors.affiliation: Department of Kinesiology, University of Wisconsin Madison, WI, USA.
authors.forename: William G
authors.initials: WG
authors.lastname: Schrage
keywords: blood flow; endothelium-dependent vasodilation; isoproterenol; neural control; smooth muscle