Effects of the nitric oxide synthase inhibitor <scp>L</scp>‐NMMA on cerebrovascular and cardiovascular responses to hypoxia and hypercapnia in humans
Bibliographic record
Abstract
Cerebral blood flow is highly sensitive to alterations in the partial pressures of O(2) and CO(2) (P(O(2)) and P(CO(2)), respectively) in the arterial blood. In humans, the extent to which nitric oxide (NO) is involved in this regulation is unclear. We hypothesized that the NO synthase (NOS) inhibitor N(G)-monomethyl-l-arginine (l-NMMA), attenuates the sensitivity of middle cerebral artery blood velocity (V(p)) to isocapnic hypoxia (end-tidal P(O(2)) = 50 Torr) and euoxic hypercapnia (end-tidal P(CO(2)) = +9 Torr above resting values) in 10 volunteers (age, 28.7 +/- 1.3 years; height, 179.2 +/- 2.4 cm; weight, 78.0 +/- 3.7 kg; mean +/- s.e.m.). The techniques of transcranial Doppler ultrasound and dynamic end-tidal forcing were used to measure(V(p)), and control end-tidal P(O(2)) and end-tidal P(CO(2)), respectively. At baseline (isocapnic euoxia), following intravenous administration of l-NMMA, mean arterial blood pressure (MAP) increased (76.3 +/- 7.3 to 86.2 +/- 9.4 mmHg) and heart rate (HR) decreased (59.5 +/- 9.0 to 55.2 +/- 9.5 beats min(-1)) but (V(p)) was unchanged. Hypoxia-induced increases in MAP, HR and were similar with and without l-NMMA (5.0 +/- 0.7 versus 7.1 +/- 1.0 mmHg, 11.5 +/- 1.4 versus 12.4 +/- 1.5 beats min(-1), 6.5 +/- 0.8 versus 6.6 +/- 0.8 cm s(-1) for DeltaMAP, DeltaHR and Delta , respectively). Hypercapnia-induced increases in MAP, HR and (V(p)) were similar with and without l-NMMA (7.4 +/- 3.1 versus 8.1 +/- 2.2 mmHg, 10.4 +/- 4.6 versus 10.0 +/- 4.2 beats min(-1), 16.5 +/- 1.5 versus 17.6 +/- 1.5 cm s(-1) for DeltaMAP, DeltaHR and Delta(V(p)) , respectively) but the sensitivity of the(V(p)) response at the removal of hypercapnia was attenuated with l-NMMA. In young healthy humans, pharmacological blockade of nitric oxide synthesis does not affect the increases in cerebral blood flow with hypoxia and hypercapnia, suggesting that nitric oxide is not required for the cerbrovascular responses to hypoxia and hypercapnia.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
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".