Ionic currents of cultured horizontal cells isolated from white perch retina.
Horizontal cells from the retinas of white perch were isolated and maintained in cell culture for 3 days to 3 wk. Four morphologically distinct types of horizontal cells could be identified in culture and were labeled types H1, H2, H3, and H4. Whole-cell patch-clamp techniques were used to study the ionic currents present in the four cell types. In all cells, depolarizing commands above threshold elicited a fast-inward current followed by an outward current. The fast-inward current was abolished by tetrodotoxin (TTX) or 0 Na+ Ringer's, indicating the current was carried by Na+. In H1, H2, and H3 cells, the outward current, carried by K+, consisted of two components: a transient current (IA), blockable with 4-aminopyridine (4-AP), tetraethylammonium (TEA), or intracellular cesium and a sustained current that could be blocked with TEA. The H4 cell had only the sustained current. An inward rectifying K+ current (anomalous rectifier) was observed in the four cell types. The current was sensitive to the extracellular K+ concentration. Its activation showed two components: an instantaneous component and a slower component. The slow component becomes faster with greater hyperpolarizations. The four cell types possessed a small, sustained Ca2+ current that, under normal conditions, was masked by the inward Na+ current and outward K+ currents.
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D000200:Action Potentials; D000818:Animals; D002118:Calcium / Q000378:metabolism; D004558:Electric Stimulation; D004594:Electrophysiology; D005399:Fishes / Q000378:metabolism*; D066298:In Vitro Techniques; D007395:Interneurons / Q000166:cytology / Q000378:metabolism*; D007473:Ion Channels / Q000378:metabolism*; D011188:Potassium / Q000378:metabolism; D012160:Retina / Q000166:cytology / Q000378:metabolism*; D012964:Sodium / Q000378:metabolism
D007473:Ion Channels; D012964:Sodium; D011188:Potassium; D002118:Calcium