title: Acute sex hormone suppression reduces skeletal muscle sympathetic nerve activity.
abstract: OBJECTIVE
  Comparisons of sympathetic nervous system activity (SNA) between young and older women have produced equivocal results, in part due to inadequate control for potential differences in sex hormone concentrations, age, and body composition. The aim of the present study was to determine the effect of a short-term reduction in sex hormones on tonic skeletal muscle sympathetic nerve activity (MSNA), an indirect measure of whole body SNA, using an experimental model of sex hormone deficiency in young women. We also assessed the independent effects of estradiol and progesterone add-back therapy on MSNA.
  
  
  METHODS
  MSNA was measured in 9 women (30±2 years; mean±SE) on three separate occasions: during the mid-luteal menstrual cycle phase, on the fifth day of gonadotropin-releasing hormone antagonist (GnRHant) administration, and after 5 days add-back of either estradiol (n=4) or progesterone (n=3) during continued GnRHant administration.
  
  
  RESULTS
  In response to GnRHant, there were significant reductions in serum estradiol and progesterone (both p<0.01) and MSNA (25.0±1.9 vs. 19.2±2.4 bursts/min, p=0.04). Continued GnRHant plus add-back estradiol or progesterone resulted in a nonsignificant decrease (19.2±1.7 vs. 12.1±1.9 bursts/min, p=0.07) or increase (16.2±1.7 vs. 21.0±6.0 bursts/min, p=0.39), respectively, in MSNA when compared with GnRHant alone.
  
  
  CONCLUSIONS
  The findings of this preliminary study suggest that short-term ovarian hormone suppression attenuates MSNA and that this may be related to the suppression of progesterone rather than estradiol.
authors.affiliation: Department of Physical Therapy, University of Massachusetts-Lowell, 3 Solomont Way, Suite 5, Lowell, MA, 01854, USA. Danielle_Day@uml.edu
authors.forename: Danielle S
authors.initials: DS
authors.lastname: Day
authors.forename: Wendolyn S
authors.initials: WS
authors.lastname: Gozansky
authors.forename: Christopher
authors.initials: C
authors.lastname: Bell
authors.forename: Wendy M
authors.initials: WM
authors.lastname: Kohrt
mesh_terms: D000328:Adult; D000367:Age Factors; D001794:Blood Pressure / Q000187:drug effects; D015232:Dinoprostone / Q000494:pharmacology; D005260:Female; D012739:Gonadal Steroid Hormones / Q000097:blood; D007987:Gonadotropin-Releasing Hormone / Q000031:analogs & derivatives* / Q000494:pharmacology; D006339:Heart Rate / Q000187:drug effects; D006727:Hormone Antagonists / Q000494:pharmacology*; D006801:Humans; D018482:Muscle, Skeletal / Q000187:drug effects*; D010120:Oxytocics / Q000494:pharmacology; D013564:Sympathetic Nervous System / Q000187:drug effects* / Q000502:physiology
chemical_list: D012739:Gonadal Steroid Hormones; D006727:Hormone Antagonists; D010120:Oxytocics; D007987:Gonadotropin-Releasing Hormone; C042691:LHRH, N-acetyl-(4-chlorophenylalanyl)(1)-(4-chlorophenylalanyl)(2)-tryptophyl(3)-arginyl(6)-alanine(10)-; D015232:Dinoprostone