Characterization of Ca <sup>2+</sup> ‐Based Action Potentials in Horizontal Cells in the Goldfish ( <i>Carassius auratus</i> ) Retina
Notice bibliographique
Résumé
About 65 years ago, the first intracellular recordings ever to be made in the retina were made in horizontal cells (HCs) of goldfish ( Carassius auratus ). These recordings were some of the first examples of graded potentials (where membrane potential changes in proportion with a stimulus), and it was assumed that outer retinal neurons did not present action potentials (APs). HCs are interneurons which provide inhibitory feedback to photoreceptors, and in vision they are responsible for improving contrast, edge detection, and color opponency. Since these first recordings, Ca 2+ ‐based APs and spontaneous increases in intracellular Ca 2+ concentration ([Ca 2+ ] i ) have been found in fish HCs, although they are poorly understood and their role in vision (if any) is unknown. We characterized spontaneous, Ca 2+ ‐based APs in isolated goldfish HCs by measuring changes in [Ca 2+ ] i and membrane potential ( V m ). Using Fura‐2 Ca 2+ imaging, we found spontaneous Ca 2+ activity characterized by transient elevation in [Ca 2+ ] i of short (seconds) and long (minutes) duration, in 157/177 cells (89%). These APs were similar in amplitude to Ca 2+ responses evoked by glutamate. APs were reversibly eliminated in Ca 2+ ‐free solutions (n=18), and were abolished by the L‐type Ca 2+ channel blocker, nifedipine (100 μM; n=5). APs were also dependent on intracellular Ca 2+ stores: they were abolished by the ryanodine receptor antagonists, ryanodine (20 μM; in 7/8 cells) and dantrolene (50 μM; n=7). The ryanodine receptor agonist, caffeine (n=10), increased AP frequency 2.8‐fold (p<0.0002) and reduced median duration (29.3 s to 18.7 s), time to peak (12.3 s to 7.8 s), and area under the curve (by 59.6%). When caffeine was co‐applied with the store‐operated channel antagonist, 2‐aminoethyldiphenyl borate (2‐APB), frequency was unaffected, further confirming a role for stores. We tracked changes in V m with whole‐cell current‐clamp recording, and with the voltage‐sensitive dye, FluoVolt. Phenotypes of APs in FluoVolt (n=6) and current‐clamp (48/57 cells; 84%) experiments displayed a sharp rise to peak, followed by a slow decline for the duration of the transient, and a steep return to baseline. In current‐clamp experiments, APs were dependent on L‐type Ca 2+ channel activity. APs were blocked by Co 2+ (5 mM; n=5) and nifedipine (100 μM; n=5), and were amplified and prolonged by the L‐type channel‐permeant ion, Ba 2+ (15 mM; n=6). In addition, APs were abolished in 6/9 cells in Ca 2+ ‐free solution. Collectively, our data suggest that activation of voltage‐dependent L‐type Ca 2+ channels leads to Ca 2+ influx, depolarization of V m , and additional Ca 2+ release from stores via ryanodine receptors. Understanding this phenomenon is a first step to elucidating a possible role for APs in vision or retinal physiology. This work also challenges the long‐held belief that outer retinal neurons do not present APs, and may lead to new paradigms about how visual information is encoded in the vertebrate retina. Support or Funding Information We acknowledge the support of the Natural Sciences and Engineering Research Council of Canada (NSERC), grant 342303. This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal .
Récupéré en direct depuis OpenAlex et désinversé. Les résumés ne sont pas conservés dans cette base de données : les index inversés représentent 8,6 Go des 9,3 Go de texte de la base, et le serveur dispose de 13 Go libres.
Comment cette classification a été obtenuedéplier
Prédiction machine sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Le volet Gemma est une étiquette directe du modèle pour chaque travail de la base, lue sur la notice réduite au titre. Le volet Codex est un classifieur appris des 10 348 étiquettes directes de Codex et calibré sur les taux pondérés de l'échantillon; les champs sans appui suffisant ne portent aucun appel Codex. Le mode candidate est l'union des deux volets; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont pas des étiquettes humaines.
Scores du classifieur distillé par catégorie (deux têtes)
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,000 | 0,000 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,000 | 0,000 |
| Études des sciences et des technologies | 0,000 | 0,000 |
| Communication savante | 0,000 | 0,000 |
| Science ouverte | 0,000 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,000 | 0,000 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule source (Gemma direct ou Codex distillé), pas un consensus.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».