Premium
Lumbar Sympathetic Nerve Activity at Rest and During Muscle Contraction: Effects of Estrogen and Nitric Oxide
Author(s) -
Just Timothy P,
DeLorey Darren S
Publication year - 2017
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.31.1_supplement.712.2
Subject(s) - endocrinology , medicine , contraction (grammar) , blood pressure , chemistry , nitric oxide
Efferent sympathetic nerve activity (SNA) is critical for the control of blood pressure and peripheral vascular resistance at rest and during exercise. Nitric oxide (NO) is known to have an inhibitory effect on efferent SNA and estrogen has been shown influence NO synthase (NOS) expression and NO bioavailability. Therefore, the purpose of this study was to investigate the hypothesis that estrogen status alters SNA at rest and during muscle contraction through an NO dependent mechanism. Female Sprague‐Dawley rats were randomly assigned to OI (n=10), OVX (n=9) or OVX‐E (n=8) groups. A bilateral ovariectomy was performed in OVX rats and a placebo or time‐release 17β‐estradiol pellet (OVX‐E) was implanted subcutaneously for 4 weeks. Rats were then anesthetized and instrumented for the measurement of blood pressure and lumbar SNA (LSNA) at rest and during hindlimb muscle contraction in control, NOS blockade (L‐NAME; 10 mg·kg −1 IV), and NOS blockade with normalization of blood pressure (hydralazine; 0.01–0.06 mg·kg −1 ·min −1 IV) conditions. In control conditions, MAP and LSNA were similar (p>0.05) in OI, OVX and OVX‐E rats at rest. LSNA increased in response to muscle contraction in all groups and LSNA was not different in OI, OVX and OVX‐E rats during muscle contraction. NOS blockade increased (p<0.05) MAP and decreased LSNA by similar magnitudes (p>0.05) in OI, OVX and OVX‐E rats at rest and during exercise. Infusion of hydralazine in the presence of NOS inhibition returned MAP to levels observed at rest and during muscle contraction in the control condition in all groups. LSNA was not different (p<0.05) in OI, OVX, OVX‐E rats at rest and during muscle contraction in the presence of NOS inhibition and hydralazine. These data suggest that estrogen status does not alter efferent sympathetic nerve activity directed to skeletal muscle at rest or during exercise. Furthermore, these data suggest that the effects of systemic NOS blockade on LSNA are not dependent on estrogen status. Support or Funding Information Natural Sciences and Engineering Research Council of Canada (NSERC), Canadian Foundation for Innovation, and Alberta Advanced Education and Technology.