Dopaminergic Mediation of the Effect of Elevated Potassium on the Release of Pro-Opiomelanocortin-Derived Peptides from the Pars intermedia of the Rat Pituitary
Bibliographic record
Abstract
The pars intermedia (PI) of the adenohypophysis synthesizes pro-opiomelanocortin (POMC), which through post-translational processing, gives rise to a group of chemically related peptides, including αMSH, ACTH, CLIP, LPHs and endorphins. We investigated the control of release of these peptides using an in vitro system. We perifused either acutely dispersed rat PI cells or intact rat neurointermediate lobes (NI). Perifusion medium was subjected to a series of bioassays (BA) and radioimmunoassays (RIA) (including MSH-BA, ACTH-BA, ACTH-RIA, αMSH-RIA, LPH-RIA) and a receptor-binding assay for morphine-like activity. Both dispersed PI cells and intact NI responded to dopamine (DA) with a dose-related and sustained decrease in release of all of the assayable peptides. The response to an 8-fold elevation in K+ in the medium (8K) differed in the dispersed PI cells and intact NI. Whereas the PI cells responded with a transient ‘spike’ of release of all of the assayable peptides, the NI responded to 8K with a sustained decrease in release of all of the assayable peptides, except for ACTH-BA. To explain this difference in response, we tested the hypothesis that in dispersed PI, 8K acts directly on the parenchymal cells to elicit a transient release of peptides, while in intact NI, 8K acts preferentially on the dopaminergic neurones in the gland to release DA. This endogenous DA then acts directly on the PI cells to inhibit release of peptides. The DA-antagonist, d-butaclamol (dBUT, 10–7–10–5M) was used to test this hypothesis. dBUT abolished the DA-induced inhibition of peptide release, and converted the inhibitory response to 8K of intact NI to the transient ‘spike’ response typical of dispersed PI cells. These results strongly support the participation of the dopaminergic arcuato-hypophyseal system in inhibitory control of the release of POMC-derived peptides from the PI.
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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 | 0.002 |
| 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 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 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".