Compartmentalization of Choline and Acetylcholine Metabolism in Cultured Sympathetic Neurons
Bibliographic record
Abstract
To determine the relative contribution of cell bodies and distal axons to the production of acetylcholine, we used retinoic acid to induce a cholinergic phenotype in compartmented cultures of rat sympathetic neurons. When [3H]choline was given to cell bodies/proximal axons for 24 h, 98% of the radiolabel was recovered as choline, phosphocholine, CDP-choline and phosphatidylcholine, whereas only 1 to 2% of the radiolabel was incorporated into acetylcholine. Choline taken up by cell bodies and transported to axons is poorly utilized for acetylcholine biosynthesis. In contrast, when distal axons were supplied with [3H]choline, 11% of the radiolabel was recovered in acetylcholine after 24 h, the remainder being incorporated into precursors/metabolites of phosphatidylcholine. The lack of acetylcholine synthesis in cell bodies/proximal axons could not be ascribed to an absence of choline acetyltransferase activity in this region of the neurons, since the specific activity of this enzyme was similar in cell bodies/proximal axons and distal axons. The rate of choline uptake by distal axons (15.3 4.4 nmol/5 min/mg protein) was approximately 10-fold greater than by cell bodies/proximal axons (1.6 0.8 nmol/5 min/mg protein). Moreover, choline uptake into distal axons was inhibited by 74.5% by hemicholinium-3, and by 80.1% by removal of Na(+) from the medium. In contrast, choline uptake by cell bodies/proximal axons was not significantly inhibited by hemicholinium-3 or Na(+) removal. These results suggest that the majority of axonal acetylcholine is synthesized in distal axons/axon terminals from choline taken up by a high-affinity choline transporter in distal axons.
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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) | 0.001 | 0.001 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| 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".