Pre‐ and postsynaptic modulation of monosynaptic reflex by GABA<sub>A</sub>receptors on turtle spinal cord
Bibliographic record
Abstract
There is growing evidence that activation of high affinity extrasynaptic GABA(A) receptors in the brain, cerebellum and spinal cord substantia gelatinosa results in a tonic inhibition controlling postsynaptic excitability. The aim of the present study was to determine if GABA(A) receptors mediating tonic inhibition participate in the modulation of monosynaptic reflex (MSR) in the vertebrate spinal cord. Using an in vitro turtle lumbar spinal cord preparation, we show that conditioning stimulation of a dorsal root depressed the test monosynaptic reflex (MSR) at long condition-test intervals. This long duration inhibition is similar to the one seen in mammalian spinal cord and it is dependent on GABA(A) as it was completely blocked by 20 microm picrotoxin (PTX) or bicuculline (BIC) or 1 microm gabazine, simultaneously depressing the dorsal root potential (DRP) without MSR facilitation. Interestingly 100 microm picrotoxin or BIC potentiated the MSR, depressed the DRP, and produced a long lasting motoneurone after-discharge. Furosemide, a selective antagonist of extrasynaptic GABA(A) receptors, affects receptor subtypes with alpha(4/6) subunits, and in a similar way to higher concentrations of PTX or BIC, also potentiated the MSR but did not affect the DRP, suggesting the presence of alpha(4/6) GABA(A) receptors at motoneurones. Our results suggest that (1) the turtle spinal cord has a GABA(A) mediated long duration inhibition similar to presynaptic inhibition observed in mammals, (2) GABA(A) receptors located at the motoneurones and primary afferents might produce tonic inhibition of monosynaptic reflex, and (3) GABA(A) receptors modulate motoneurone excitability reducing the probability of spurious and inappropriate activation.
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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".