Acute hyperoxia elicits decreases in muscle sympathetic nerve activity and action potential activation in a sex-dependent manner
Bibliographic record
Abstract
Acute hyperoxia (100 % oxygen) has been shown to reduce muscle sympathetic nerve activity (MSNA), suggesting that hyperoxia could be a potential strategy for lowering blood pressure. However, the efficacy of hyperoxia to reduce blood pressure (e.g., mean arterial pressure; MAP) remains unclear. Therefore, we compared MSNA and MAP responses to acute hyperoxia (1-min pokilocapnic + 3-min, PetO 2 O 2 + 300 Torr) between 18 females and 13 males. Baseline integrated total MSNA was not different between females and males (24 ± 7 vs 23 ± 8 bursts/min, respectively; P = 0.68) while MAP was lower in females than males (85 ± 7 vs 93 ± 7 mmHg; P < 0.01). Overall, hyperoxia evoked reductions in MSNA burst frequency (BF; P = 0.02) but not burst amplitude (BA; P = 0.82) or total MSNA (=BF ∗ BA; P = 0.26), To further probe these responses, 1-min nadir total MSNA response to hyperoxia were extracted within each participant. Total MSNA was reduced from baseline during nadir hyperoxia only in males (sex ∗ cond: P = 0.04). Females exhibited a bimodal distribution of sympatho-inhibitors (F I ) and non-inhibitors (F NI ). F NI demonstrated limited reductions in BF ( P = 0.11 vs inhibitors) coupled with increases in BA ( P < 0.01 vs inhibitors), resulting in no net change in total MSNA (P < 0.01 vs inhibitors). Mechanistically, action potential (AP) detection analyses revealed that F NI increased AP firing during hyperoxia (baseline: 313 ± 172 vs hyperoxia: 404 ± 192 spikes/min; P = 0.02), whereas hyperoxia blunted AP firing in F I (baseline: 387 ± 263 vs hyperoxia: 267 ± 199 spikes/min; P = 0.02). In sum, approximately 50 % of healthy females responded to acute hyperoxia with unexpected increases in AP firing. These data may suggest that benefit of hyperoxia as a sympatho-inhibitor may be limited in young and healthy females.
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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 | 0.001 |
| Insufficient payload (model declined to judge) | 0.005 | 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".