AMPA receptor modulation in previously frozen mouse brain sections: Opposite effects of calcium in the cortex and hippocampus
Bibliographic record
Abstract
Various forms of synaptic plasticity in the brain have been proposed to result from modifications in the properties of glutamate receptors by calcium-dependent mechanisms. In the present study, changes in glutamate receptors elicited by calcium treatment of previously frozen mouse brain sections were evaluated by qualitative as well as quantitative analysis of tritiated ligand binding to both alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionate (AMPA) and N-methyl-D-aspartate (NMDA) glutamate receptor subtypes. Quantitative analysis revealed that 3H-AMPA binding was reduced in a dose-dependent manner by calcium in the cerebral cortex and striatum formations. However, an opposite change in AMPA receptor properties was observed in the hippocampus, as calcium generated an increase of AMPA binding in all hippocampal fields. Analysis of the saturation kinetics of 3H-AMPA binding showed that the calcium-induced augmentation of AMPA binding in the stratum radiatum of the CA1 region was due to an alteration in the maximal number of sites, while the reduction of binding elicited by calcium in the cortex appeared to be due to modified AMPA receptor affinity. Calcium-induced downregulation of AMPA receptor affinity in the cortex and striatum was affected by baicalein, a selective inhibitor of the lipoxygenase pathways of arachidonic acid metabolism, whereas the same inhibitor did not modify calcium-mediated upregulation of receptor number in the CA1 region of the hippocampus. On the other hand, the effect of calcium appeared to be specific for the AMPA receptor, as the same treatment did not affect glutamate binding to the NMDA glutamate receptor subtype. Our results suggest the possibility that, depending on the brain regions, calcium ions may generate opposite modulation of AMPA receptor properties. Because the regulation of AMPA receptors by calcium-dependent enzymes has been implicated in synaptic plasticity, our results suggest that regional variations in the effect of calcium on AMPA binding account for differential plasticity at glutamatergic synapses.
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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 | 0.001 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| 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".