Differential modulation of rod and cone calcium currents in tiger salamander retina by D2 dopamine receptors and cAMP
Bibliographic record
Abstract
Synaptic transmission from vertebrate photoreceptors involves activation of L-type calcium currents (ICa). Dopamine is an important circadian neuromodulator in the retina and photoreceptors possess D2 dopamine receptors. We examined modulation of ICa by dopamine and cAMP in retinal slices and isolated cells of larval tiger salamander. Results show that dopamine and a D2 agonist, quinpirole, enhanced ICa in rods and red-, blue- and UV-sensitive small single cones but inhibited ICa in red-sensitive large single cones. A D1 agonist, SKF-38393, was without effect. Quinpirole effects were blocked by pertussis toxin (PTx) pretreatment indicating involvement of PTx-sensitive G-proteins. Like dopamine, inhibition of cAMP-dependent protein kinase (PKA) by Rp-cAMPS enhanced ICa in rods and small single cones, but inhibited ICa in large single cones. In contrast, forskolin and Sp-cAMPS, which stimulate PKA, inhibited ICa in rods and small single cones but enhanced ICa in large single cones. Sp-cAMPS also occluded effects of quinpirole. These results suggest that D2 receptors modulate ICa via inhibition of cAMP. Differences among the responses of photoreceptors to cAMP are consistent with the possibility that small single cones and rods may possess different Ca2+ channel subtypes than large single cones. The results with dopamine and quinpirole showing inhibition of ICa in large single cones and enhancement of rod ICa were unexpected because previous studies have shown that dopamine suppresses rod inputs and enhances cone inputs into second-order neurons. The present results therefore indicate that the dopaminergic enhancement of cone inputs does not arise from modulation of photoreceptor ICa.
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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".