Localisation of VIP-binding sites exhibiting properties of VPAC receptors in chromaffin cells of rainbow trout (<i>Oncorhynchus mykiss</i>)
Bibliographic record
Abstract
The current model for the neuronal control of catecholamine release from piscine chromaffin cells advocates that the neurotransmitters vasoactive intestinal polypeptide (VIP) and pituitary adenylate cyclase-activating polypeptide (PACAP) are co-released with acetylcholine from preganglionic fibres upon nerve stimulation. Both VIP and PACAP elicit the secretion of exclusively adrenaline from rainbow trout chromaffin cells, which presumably arises from the activation of VPAC type receptors. Thus, the goals of the present study were (1) to localise VPAC receptors in the chromaffin cell fraction of the posterior cardinal vein (PCV) of trout and (2) to test the hypothesis that the selective secretion of adrenaline elicited by VIP could be explained by the absence of the VPAC receptors from the noradrenaline-containing cells. Fluorescent labelling of chromaffin cells using aldehyde-induced fluorescence of catecholamines and antisera raised against dopamine beta-hydroxylase (DbetaH) revealed a distinct layer of chromaffin cells lining the walls of the PCV. Furthermore, specific VIP-binding sites were demonstrated on chromaffin cells using a biotinylated VIP that was previously established as being bioactive. Although multiple labelling experiments revealed that a number of DbetaH-positive cells were immunonegative for phenylethanolamine N-methyl transferase (PNMT; noradrenaline-containing cells versus adrenaline-containing cells, respectively), labelling of VIP-binding sites was similar to that of DbetaH labelling, suggesting that all chromaffin cells possess VIP-binding sites. Pharmacological assessment of the VIP-binding sites indicated that they exhibited characteristics of VPAC receptors. Specifically, the labelling of VIP-binding sites was prevented after pre-treatment of PCV tissue sections with unlabelled VIP, PACAP or the specific VPAC receptor antagonist VIP 6-28. By contrast, sections pre-treated with the PAC(1) receptor blocker PACAP 6-27 displayed normal labelling of VIP-binding sites. Finally, partial cDNA clones for the trout VPAC(1) and VPAC(2) receptor were obtained and sequenced. Tissue distribution experiments using RT-PCR revealed the presence of VPAC(1) receptor mRNA but not that of the VPAC(2) receptor in the PCV tissue. The results provide direct evidence that VIP and PACAP can elicit the secretion of adrenaline from the chromaffin tissue via specific VIP-binding sites that exhibit properties of VPAC receptors. However, the selective secretion of adrenaline by VIP or PACAP cannot be explained by a lack of VIP-binding sites on the noradrenaline-containing cells.
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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 | 0.000 |
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".