Developmental changes in trigeminal motoneuron properties in the American bullfrog, <i>Lithobates catesbeianus</i>
Bibliographic record
Abstract
In frogs, the neural circuits generating gill and lung ventilation are distinct, yet their activities converge on the same groups of motoneurons located in the brainstem, including the trigeminal, hypoglossal, and vagal motoneurons. Because lung ventilation requires more forceful contractions to “push” air back into the lungs, it is plausible that the basic electrophysiological properties of respiratory motoneurons that activate the buccal musculature change during tadpole development in ways that facilitate lung ventilation; however, this hypothesis remains untested. To address this issue we used an electrophysiological approach to compare the functional properties of trigeminal motoneurons between pre‐metamorphic tadpoles and adult frogs. Retrograde labelling of trigeminal motoneurons was performed with the fluorescent marker DiI at least 14 days prior to experiments. Using a coronal slice preparation, we performed whole‐cell recordings from fluorescently‐tagged cells to measure basic motoneurons properties. Electrophysiological characterization was performed by measuring membrane potential responses to steps of current injections. Unexpectedly, the trigeminal motor pool seemed to be composed of two distinct motoneuron populations based on cell size. Resting membrane potential did not differ between populations or developmental stages (~−54 mV). The smaller cells were generally more excitable than the larger ones as indicated by a lower rheobase (49 ± 7 versus 275 ± 48 pA) and a more hyperpolarized action potential threshold (−43 ± 2 versus −38 ± 2 mV). The density of the hyperpolarization‐activated inward current ( I h ) was more than 10 times greater in smaller cells. With regards to development, recordings revealed lower membrane resistance in frogs than tadpoles; this developmental change was more important in the smaller cells. Finally, the amplitude of evoked action potentials was greater in frog motoneurons than tadpoles; the developmental augmentation was more important in the smaller cells. While morphometric assessment of each cell type is underway, the cell heterogeneity observed in the trigeminal motor nucleus raises the possibility that the different cell types are associated with different motor commands (gill versus lung ventilation). Owing to the developmental changes observed in the smaller cells, we propose that this population is associated with the production of air breaths. Support or Funding Information Supported by Natural Sciences and Engineering Research Council of Canada
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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 | 0.001 |
| 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".