Seizure‐like discharges induced by 4‐aminopyridine in the olfactory system of the in vitro isolated guinea pig brain
Bibliographic record
Abstract
PURPOSE: The study of the interactions leading to network- or region-specific propagation of seizures is crucial to understand ictogenesis. We have recently found that systemic (arterial) application of the potassium channel blocker, 4-aminopyridine (4AP), induces different and independent seizure activities in olfactory and in limbic structures. Here, we have characterized the network and cellular features that support 4AP-induced seizure-like events in the olfactory cortex. METHODS: Simultaneous extracellular recordings were performed from the piriform cortex, the entorhinal cortex, the olfactory tubercle, and the amygdala of the in vitro isolated guinea pig brain preparation. Intracellular, sharp electrode recordings were obtained from neurons of different layers of the region of ictal onset, the piriform cortex. Seizure-like discharges were induced by both arterial perfusion and local intracortical injections of 4AP. KEY FINDINGS: Arterial application of 4AP induces independent seizure activities in limbic and olfactory cortices. Both local applications of 4AP and cortico-cortical disconnections demonstrated that region-specific seizure-like events initiated in the primary olfactory cortex and propagate to anatomically related areas. Seizures induced by arterial administration of 4-AP are preceded by runs of fast activity at circa 30-40 Hz and are independently generated in the hemispheres. Simultaneous extracellular and intracellular recordings in the piriform cortex revealed that the onset of seizure correlates with (1) a gradual amplitude increase of fast activity runs, (2) a large intracellular depolarization with action potential firing of superficial layer neurons, and (3) no firing in a subpopulation of deep layers neurons. During the ictal event, neuronal firing was abolished for 10-30 s in all neurons and gradually restored and synchronized before seizure termination. SIGNIFICANCE: Our data show that olfactory neuronal networks sustain the generation of seizure-like activities that are independent from those observed in adjacent and connected limbic cortex regions. The data support the concept that functionally and anatomically hard-wired networks generate region-specific seizure patterns that could be substrates for system epilepsy.
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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".