Lumbar Sympathetic Nerve Activity at Rest and During Muscle Contraction: Effects of Estrogen and Nitric Oxide
Bibliographic record
Abstract
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.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".