Phenoxybenzamine Selectively and Irreversibly Inactivates Dopaminergic D <sub>2</sub> Receptors on Primary Cultured Rat Lactotrophs
Bibliographic record
Abstract
Lactotrophs have several different kinds of receptors, such as dopaminergic D2, somatostatin, angiotensin II and thyrotropin-releasing hormone receptors, which stimulate or inhibit prolaction release. We have studied the specificity of phenoxybenzamine on receptors in lactotrophs. Phenoxybenzamine is a β-haloalkylamine which alkylates chemically active radicals such as hydroxy, sulfhydryl, and amino groups. This alkylation is an irreversible chemical reaction in contrast to the receptor-secretagogue complex which is present in a state of dynamic equilibrium. Primary cultured rat adenohypophyseal cells were used in this study. A dose-response relationship was examined between concentrations of phenoxybenzamine pretreatment and prolactin release using a monolayer cell culture system. The inhibitory action of dopamine (10 µmol/l) on the control group (13.0 ± 0.1 ng/ml or 86% inhibition relative to the control) was significantly higher than on the 0.1-µmol/l phenoxybenzamine-pretreated group (39.0 ± 0.2 ng/ml or 58% inhibition relative to the control), but the stimulatory effect of thyrotropin-releasing hormone on prolactin release was not significantly affected up to a 10-µmol/l phenoxybenzamine pretreatement as compared with the control group. We thus selected a phenoxybenzamine concentration of 0.1 µmol/l for the next series of perifusion experiments in order to examine dynamic changes in prolactin release. The basal prolaction release was decreased to almost half by phenoxybenzamine pretreatment. The inhibitory action of dopamine (0.1 µmol/l containing 0.1 mmol/l ascorbic acid) was significantly less in the phenoxybenzamine-pretreated group (68% of the basal prolactin concentration) than in the control group (31% of the basal concentration). However, the relative actions of somatostatin, thyrotropin-releasing hormone, angiotensin II, and dibutyryl adenosine 3’,5’-cyclic adenosine monophosphate were not significantly affected by the phenoxybenzamine pretreatment. These observations suggest that phenoxybenzamine is relatively selective to dopaminergic D2 receptors in primary cultured lactotrophs. The basal prolactin release in the phenoxybenzamine-pretreated group increased steadily during the experimental period. The basal prolactin release was doubled within 153.7 ± 22.3 min.
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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) | 0.000 | 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 | 0.001 |
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".