Pressor Response to β <sub>1</sub> - and β <sub>2</sub> -Blockers in Conscious Rats Treated with Phentolamine
Bibliographic record
Abstract
The purpose of this study was to examine the conditions whereby β-blockers cause a pressor response in conscious, unrestrained rats: (1) whether β-blockers cause a pressor response in rats subjected to, or not subjected to, nonselective α-blockade with phentolamine; (2) whether the pressor response to β-blockers is due to the blockade of vasodilator β2-adrenoceptors, and (3) whether it is due to an acute increase in the release of adrenaline (A) and noradrenaline (NA). In the first series of experiments cumulative dose-response curves for propranolol, atenolol and ICI 118,551, nonselective β-, β1 and β2-selective antagonists, respectively, were constructed in rats subjected to a continuous intravenous infusion of phentolamine. The administration of each of the β-antagonists caused a significant dose-dependent increase in mean arterial pressure (MAP). The ED5o values for the increase in MAP were found to be 3.6 ± 0.8, 10 ± 2.6 and 4.6 ± 0.8 μg/kg for propranolol, atenolol and ICI 118,551, respectively. In the second series of experiments, a single bolus injection of a selective or nonselective β-antagonist or saline vehicle was given to rats subjected to a continuous intravenous infusion of phentolamine. Plasma levels of A and NA were determined in the control condition, during the infusion of phentolamine and again after the injection of a β-antagonist. The infusion of phentolamine significantly decreased MAP and increased plasma levels of A and NA. During the infusion of phentolamine, a single bolus injection of propranolol (100 μg/kg), atenolol (100 μg/kg) and ICI 118,551 (30 μg/kg) significantly increased MAP, but did not alter NA and A levels relative to the injection of saline. It is concluded that (1) the pressor response to β-blockers occurs only in rats subjected to α-blockade, (2) pressor response also occurs with a selective β1-antagonist, atenolol, used at doses that do not alter the response of a selective β2-agonist and therefore it is not due to the blockade of vasodilator β2-adrenoceptors, and (3) it is not due to an acute increase in the release of catecholamines.
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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) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.002 |
| Insufficient payload (model declined to judge) | 0.002 | 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".