Light-Evoked Calcium Responses of Isolated Melanopsin-Expressing Retinal Ganglion Cells
Bibliographic record
Abstract
A small number (<2%) of mammalian retinal ganglion cells express the photopigment melanopsin and are intrinsically photosensitive (ipRGCs). Light depolarizes ipRGCs and increases intracellular calcium levels ([Ca2+]i) but the signaling cascades underlying these responses have yet to be elucidated. To facilitate physiological studies on these rare photoreceptors, highly enriched ipRGC cultures from neonatal rats were generated using anti-melanopsin-mediated plate adhesion (immunopanning). This novel approach enabled experiments on isolated ipRGCs, eliminating the potential confounding influence of rod/cone-driven input. Light induced a rise in [Ca2+]i (monitored using fura-2 imaging) in the immunopanned ipRGCs and the source of this Ca2+ signal was investigated. The Ca2+ responses were inhibited by 2-aminoethoxydiphenyl borate, SKF-96365 (1-2-(4-methoxyphenyl)-2-[3-(4-methoxyphenyl)propoxy]ethyl-1H-imidazole), flufenamic acid, lanthanum, and gadolinium, consistent with the involvement of canonical transient receptor potential (TRP) channels in ipRGC phototransduction. However, the contribution of direct Ca2+ flux through a putative TRP channel to ipRGC [Ca2+]i was relatively small, as most (approximately 90%) of the light-induced Ca2+ responses could be blocked by preventing action potential firing with tetrodotoxin. The L-type voltage-gated Ca2+ channel (VGCC) blockers verapamil and (+)-cis-diltiazem significantly reduced the light-evoked Ca2+ responses, while the internal Ca2+ stores depleting agent thapsigargin had negligible effect. These results indicate that Ca2+ influx through VGCCs, activated after action potential firing, was the primary source for light-evoked elevations in ipRGC [Ca2+]i. Furthermore, concurrent Ca2+ imaging and cell-attached electrophysiological recordings demonstrated that the Ca2+ responses were highly correlated to spike frequency, thereby establishing a direct link between action potential firing and somatic [Ca2+]i in light-stimulated ipRGCs.
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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) | 0.001 | 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 | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.002 | 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".