High Concentrations of Dopamine and Epinephrine Protect Dopaminergic D <sub>2</sub> Receptors from Inactivation by Phenoxybenzamine on Primary Cultured Rat Lactotrophs
Bibliographic record
Abstract
The effect of a high concentration of catecholamines on phenoxybenzamine pretreatment was examined. The efficacy of the pretreatments was monitored by testing the inhibitory action of dopamine on prolactin release. Phenoxybenzamine is a beta-haloalkylamine which alkylates and irreversibly inactivates adrenergic alpha-receptors in smooth muscle. Dopaminergic D2 receptors share several common characteristics with the alpha-receptors. Primary cultured male rat pituitary cells were used. After phenoxybenzamine (0.1 mumol/l) pretreatment, the inhibitory action of dopamine on prolactin release was significantly reduced in a perifusion system. When the cells were pretreated with phenoxybenzamine in medium containing 0.1 or 1 mmol/l dopamine, the 0.1-mmol/l dopamine did not change the effect of phenoxybenzamine on inactivation of the receptors, but the 1-mmol/l dopamine eliminated the effect of phenoxybenzamine pretreatment. These observations were confirmed with a static monolayer culture system. The observations illustrate that a high concentration of dopamine forms a D2 receptor-dopamine complex and protects the D2 from inactivation by phenoxybenzamine. When the cells were pretreated with 0.1 mumol/l phenoxybenzamine in a medium containing 1 mmol/l epinephrine, the effect of the phenoxybenzamine was also eliminated, suggesting that a sufficient amount of D2 receptor-epinephrine complex was formed to protect the receptor from inactivation. The hormone release in response to a secretagogue depends on its affinity and intrinsic activity. It is, therefore, suggested that the intrinsic activity of epinephrine is much lower than that of dopamine on prolactin release, since the D2 receptor-epinephrine complex is as stable as the D2 receptor-dopamine complex, and the inhibitory action of epinephrine on prolactin release is less than 10% of that of dopamine.(ABSTRACT TRUNCATED AT 250 WORDS)
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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".