Light-dependent channels from excised patches of Limulus ventral photoreceptors are opened by cGMP.
The identity of the second messenger that directly activates the light-dependent conductance in invertebrate photoreceptors remains unclear; the available evidence provides some support for cGMP and Ca2+. To resolve this issue we have applied these second messengers to membrane patches excised from the light-sensitive lobe of Limulus ventral photoreceptors. Our results show that these patches contain channels that can be opened by cGMP, but not by Ca2+. These cGMP-activated channels closely resemble the channels activated by light in cell-attached patches. This evidence suggests that cGMP is the messenger that opens the light-dependent channel in invertebrate photoreceptors.
Bacigalupo
J
J
Department of Biology, Faculty of Sciences, University of Chile, Santiago.
Johnson
E C
EC
Vergara
C
C
Lisman
J E
JE
D000818:Animals; D002118:Calcium / Q000502:physiology; D006152:Cyclic GMP / Q000502:physiology*; D004553:Electric Conductivity; D006737:Horseshoe Crabs / Q000502:physiology*; D066298:In Vitro Techniques; D015640:Ion Channel Gating / Q000502:physiology*; D007473:Ion Channels / Q000502:physiology*; D008027:Light; D008564:Membrane Potentials; D010786:Photoreceptor Cells / Q000502:physiology*; D014785:Vision, Ocular
D007473:Ion Channels; D006152:Cyclic GMP; D002118:Calcium