Regional distribution of cGMP-activated ion channels in the plasma membrane of the rod photoreceptor.
In patch-clamp recordings from excised membrane patches, the distribution of cGMP-activated channels in the plasma membrane of the rod photoreceptor was examined. These channels have been shown to be the light-sensitive channels that carry the inward dark current in the rod outer segment, where phototransduction occurs (Matthews, 1987); thus, they are centrally involved in photoreceptor transduction. In the outer segment, cGMP-activated channels were present at high density. In the inner segment, cGMP-activated channels were also present, but their density was much lower than in the outer segment. Calcium-activated potassium channels had the opposite distribution, with a higher density in the inner segment. The results suggest that there is a barrier preventing the unrestricted spread of membrane proteins between the inner and outer segments.
Watanabe
S
S
Department of Neurobiology and Behavior, State University of New York, Stony Brook 11794.
Matthews
G
G
D000818:Animals; D002024:Bufo marinus; D002118:Calcium / Q000494:pharmacology; D002462:Cell Membrane / Q000502:physiology; D006152:Cyclic GMP / Q000494:pharmacology*; D004553:Electric Conductivity; D007473:Ion Channels / Q000502:physiology*; D010786:Photoreceptor Cells / Q000502:physiology* / Q000648:ultrastructure; D011188:Potassium / Q000502:physiology; D012374:Rod Cell Outer Segment / Q000502:physiology
D007473:Ion Channels; D006152:Cyclic GMP; D011188:Potassium; D002118:Calcium