Subpopulation of Dorsal Horn Neurons Displays Enhanced N -methyl-d-aspartate Receptor Function after Chronic Morphine Exposure
Bibliographic record
Abstract
BACKGROUND: Morphine tolerance may be attributed to enhancement of glutamatergic neurotransmission, in particular to increased function of the N-methyl-D-aspartate (NMDA) receptor. The cellular mechanisms responsible for these changes remain poorly defined. The authors identified and characterized a specific subpopulation of dorsal horn neurons, displaying NMDA receptor plasticity in response to chronic morphine administration. METHODS: The authors undertook current clamped and voltage clamped recordings of NMDA receptor-mediated responses from cultured rat dorsal horn neurons that were untreated or treated for 7 days with 1 or 100 microm morphine. RESULTS: Smaller (capacitance < or = 22 pF), tonic firing neurons showed a significantly enhanced NMDA receptor-mediated peak current after prolonged morphine treatment, whereas larger and phasic firing neurons showed no enhancement. With high-concentration but not low-concentration morphine treatment, Mg2+ blockade of NMDA receptors at resting membrane potentials was reduced. Furthermore, the chronic opioid-induced increase in NMDA current was attenuated by pretreatment with either a mu-opioid receptor inhibitor (naloxone) or an NMDA receptor inhibitor (2-amino-5-phosphonovalerate) (low-concentration > high-concentration morphine). CONCLUSIONS: In an electrophysiologically defined subpopulation of dorsal horn neurons, enhanced NMDA receptor function after chronic morphine exposure was shown to be mechanistically dependent on morphine concentration and sensitive to both NMDA and mu-opioid receptor antagonism. Therefore, these changes observed in this population of sensory spinal neurons can be used to study the development and prevention of opioid tolerance described in multiple laboratory and clinical reports.
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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 | 0.000 | 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 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".