Dopamine receptor blockade improves pulmonary gas exchange but decreases exercise performance in healthy humans
Bibliographic record
Abstract
Key points At rest, dopamine induces recruitment of intrapulmonary arteriovenous anastomoses (IPAVA) and increases venous admixture (i.e. ). Dopamine increases during exercise, and may be partly responsible for exercise‐induced IPAVA recruitment. In this study, we antagonized dopamine receptors with metoclopramide, and observed improved pulmonary gas exchange but no difference in IPAVA recruitment during exercise. Dopamine blockade decreased cardiac output at peak exercise, resulting in decreased exercise performance. Increasing endogenous dopamine is important for the normal healthy response to exercise. Abstract Pulmonary gas exchange, as evaluated by the alveolar–arterial oxygen difference (A‐a ), is impaired during intense exercise, and has been correlated with recruitment of intrapulmonary arteriovenous anastomoses (IPAVA) as measured by agitated saline contrast echocardiography. Previous work has shown that dopamine (DA) recruits IPAVA and increases venous admixture ( ) at rest. As circulating DA increases during exercise, we hypothesized that A‐a and IPAVA recruitment would be decreased with DA receptor blockade. Twelve healthy males (age: 25 ± 6 years, : 58.6 ± 6.5 ml kg −1 min −1 ) performed two incremental staged cycling exercise sessions after ingestion of either placebo or a DA receptor blocker (metoclopramide 20 mg). Arterial blood gas, cardiorespiratory and IPAVA recruitment (evaluated by agitated saline contrast echocardiography) data were obtained at rest and during exercise up to 85% of . On different days, participants also completed incremental exercise tests and exercise tolerance (time‐to‐exhaustion (TTE) at 85% of ) with or without dopamine blockade. Compared to placebo, DA blockade did not change O 2 consumption, CO 2 production, or respiratory exchange ratio at any intensity. At 85% , DA blockade decreased A‐a , increased arterial O 2 saturation and minute ventilation, but did not reduce IPAVA recruitment, suggesting that positive saline contrast is unrelated to A‐a . Compared to placebo, DA blockade decreased maximal cardiac output, and TTE. Despite improving pulmonary gas exchange, blocking dopamine receptors appears to be detrimental to exercise performance. These findings suggest that endogenous dopamine is important to the normal cardiopulmonary response to exercise and is necessary for optimal high‐intensity exercise performance.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 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) | 0.000 | 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 teacher head, 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".