Functional NMDA Receptor Subtype 2B Is Expressed in Astrocytes after Ischemia<i>In Vivo</i>and Anoxia<i>In Vitro</i>
Bibliographic record
Abstract
NMDA-type glutamate receptors play a critical role in neuronal synaptogenesis, plasticity, and excitotoxic death. Recent studies indicate that functional NMDA receptors are also expressed in certain glial populations in the normal brain. Using immunohistochemical methods, we detected the presence of the NMDA receptor 2B (NR2B) subunit of the NMDA receptor in neurons but not astrocytes in the CA1 and subicular regions of the rat hippocampus. However, after ischemia-induced neuronal death in these regions, double immunohistochemical labeling revealed that NR2B subunits colocalized with the astrocyte marker glial fibrillary acid protein and with NR1 subunits that are required for functional NMDA receptors. NR2B expression was first observed 3 d after ischemia and reached a peak at 28 d. At 56 d, only a few NR2B-expressing astrocytes were still present. In vitro, when postnatal hippocampal cultures were subjected to 5 min of anoxia, it resulted in NR2B expression on astrocytes in the glial feed layer. Imaging of intracellular calcium with postanoxic cultures and astrocytes isolated acutely from the ischemic hippocampus revealed a rise in intracellular [Ca2+] after stimulation with the specific agonist NMDA. The response could be blocked reversibly with the competitive antagonist 2-amino-5-phosphonovalerate and attenuated by the NR2B-selective antagonist ifenprodil. Control astrocytes were not responsive to NMDA but responded to glutamate. An understanding of the role of astrocytes that express functional NMDA receptors in response to ischemia may guide development of novel stroke therapies.
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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".