Intrinsic optical signals in the rat optic nerve: Role for K<sup>+</sup> uptake via NKCC1 and swelling of astrocytes
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Bibliographic record
Abstract
Measurements of extracellular space volume and imaging of intrinsic optical signals (IOSs) have shown that neuronal activity increases light transmittance by causing cellular swelling. However, the cellular mechanisms underlying these volume changes and the contribution of astrocyte swelling to the changes in tissue volume are unclear. In this study, we have investigated IOSs in optic nerves to analyze the mechanisms contributing to these signals in a system consisting of only axons and glial cells. We examined both intact optic nerves and enucleated optic nerves, which contained no axons and consisted primarily of astrocytes. Electrical stimulation of intact optic nerves evoked an increase in light transmittance, which was graded with increasing stimulation frequency and was mimicked by raising extracellular K(+) concentration ([K(+)](o)). The stimulation-induced IOS grew in amplitude and had a time course similar to extracellular space shrinkage. Tetrodotoxin (TTX) blocked the electrically induced but not the high K(+)-induced IOS. In enucleated nerves, light transmittance progressively increased in higher [K(+)](o). The high [K(+)](o)-induced IOSs were reversibly depressed by furosemide and bumetanide, antagonists for Na-K-2Cl cotransport, but were unaltered by TTX. We also used a monoclonal antibody to the NKCC1 form of the Na-K-2Cl cotransporter to show that NKCC1 is expressed in optic nerves as shown in Western blotting and is colocalized in GFAP immunopositive astrocytes. In summary, these results indicated that KCl uptake into astrocytes via an Na-K-2Cl cotransporter during raised [K(+)](o) contributes to the generation of cellular swelling and the intrinsic optical signals.
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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 | 0.000 |
| 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) | 0.000 | 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 it