Effect of ions on the light-sensitive current in retinal rods.
The effect of ions on the light-sensitive current of retinal rods was studied by sucking the inner segment into a tightly fitting capillary with the outer segment projecting into a flowing solution. This new method showed that the light-sensitive pathway, in which Na+ is the normal carrier of current, has an ionic selectivity different from that of other known sodium channels. Externàl calcium has a striking effect on the current, which increased about 20-fold when all calcium was removed. Reducing the sodium concentration gradient greatly prolonged the response to a flash of light, as would be expected if internal calcium blocks sodium channels and if light releases calcium which is subsequently extruded by a sodium-calcium exchange mechanism.
D000818:Animals; D002024:Bufo marinus; D002118:Calcium / Q000502:physiology; D004553:Electric Conductivity; D066298:In Vitro Techniques; D007473:Ion Channels / Q000502:physiology; D008027:Light; D008274:Magnesium / Q000502:physiology; D010786:Photoreceptor Cells / Q000502:physiology* / Q000528:radiation effects; D012964:Sodium / Q000502:physiology*
D007473:Ion Channels; D012964:Sodium; D008274:Magnesium; D002118:Calcium