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 β<sub>2</sub>-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-, β<sub>1</sub> and β<sub>2</sub>-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 ED<sub>5</sub>o 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 β<sub>1</sub>-antagonist, atenolol, used at doses that do not alter the response of a selective β<sub>2</sub>-agonist and therefore it is not due to the blockade of vasodilator β<sub>2</sub>-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 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 | 0.000 | 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) | 0.000 | 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".