Membrane permeability of trace amines: Evidence for a regulated, activity-dependent, nonexocytotic, synaptic release
Bibliographic record
Abstract
Both pre- and post-synaptic effects of trace amines have been demonstrated. The putative intracellular location of Trace Amine-Associated Receptors necessitate that membrane transport processes be present in order for post-synaptic effects to occur. Here we examine the ability of trace amines to cross synthetic (Fluorosomes) and native (synaptosomes) lipid bilayer membranes. Trace amines readily crossed Fluorosome membranes by simple diffusion, p-tyramine (P = 0.01) and tryptamine (P = 0.0004) showing significantly faster diffusion than dopamine and 5-HT, respectively, with diffusion half-lives of 13.5 ± 4.1 (p-tyramine) and 6.8 ± 0.7 seconds (tryptamine). Similarly, release of [(3) H]p-tyramine and [(3) H]2-phenylethylamine from pre-loaded synaptosomes occurred significantly quicker than did [(3) H]dopamine (P = 0.0001), with half lives of 38.9 (p-tyramine), 7.8 (2-phenylethylamine) and 133.6 seconds (dopamine). This was, however, significantly slower than the diffusion mediated passage across Fluorosome membranes (P = 0.0001), suggesting a role for transporters in mediating trace amine release. Further, a pronounced shoulder region was observed in the synaptosome [(3) H]p-tyramine release curve, suggesting that multiple processes regulate release. No such shoulder region was present for [(3) H]dopamine release. Surprisingly, both [(3) H]p-tyramine (P = 0.001) and [(3) H]2-phenylethylamine (P = 0.0001) release from synaptosomes was significantly decreased under depolarizing conditions. As expected, depolarization significantly increased [(3) H]dopamine release. The data presented indicate that the release of p-tyramine and 2-phenylethylamine from neuronal terminals occurs by a different mechanism than dopamine, and does not involve classical exocytosis. The data are consistent with an initial release of trace amines by simple diffusion, followed by an activity-dependent regulation of synaptic levels via one or more transporter proteins.
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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 | 0.001 |
| 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 | 0.001 | 0.001 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.001 | 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".