GABA receptors and prepulse inhibition of acoustic startle in mice and rats
Bibliographic record
Abstract
The acoustic startle reflex is strongly inhibited by a moderate-intensity acoustic stimulus that precedes the startling stimulus by roughly 10-1000 ms (prepulse inhibition, PPI). At long interstimulus intervals (ISIs) of 100-1000 ms, PPI in rats is reduced by the muscarinic receptor antagonist scopolamine. Here, we studied the role of GABA receptors in PPI at full ISI ranges in both mice and rats. In B6 mice, PPI begins and ends at shorter ISIs (4 and 1000 ms, respectively) than in Wistar rats (8 and 5000 ms). The GABA(A) antagonist bicuculline (1 mg/kg i.p.) reduced PPI at ISIs near the peak of PPI in both rats and mice. The GABA(B) antagonist phaclofen (10 or 30 mg/kg i.p. in rats or mice, respectively) reduced PPI only at long ISIs, similar to the effects of the muscarinic antagonist scopolamine (1 mg/kg i.p.). The effects of phaclofen and scopolamine were additive in rats, suggesting independent effects of GABA(B) and muscarinic receptors. Patch-clamp recordings of startle-mediating PnC (nucleus reticularis pontis caudalis) giant neurons in rat slices show that EPSCs evoked by either trigeminal or auditory fiber stimulation were inhibited by the GABA(A/C) agonist muscimol or the GABA(B) agonist baclofen via postsynaptic mechanisms. Hyperpolarization of PnC neurons by muscimol was reversed with bicuculline, indicating that postsynaptic GABA(A) receptors strongly inhibit PnC giant neurons needed for startle. Therefore, GABA receptors on PnC giant neurons mediate a substantial part of PPI, with GABA(A) receptors contributing at the peak of PPI, and GABA(B) receptors adding to muscarinic effects on PPI at long ISIs.
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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 | 0.003 |
| 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 | 0.001 |
| 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".