Light-dependent channels from excised patches of Limulus ventral photoreceptors are opened by cGMP

  1. J Bacigalupo,
  2. E C Johnson,
  3. C Vergara, and
  4. J E Lisman
  1. Department of Biology, Faculty of Sciences, University of Chile, Santiago.

Abstract

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.

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  1. PNAS September 15, 1991 vol. 88 no. 18 7938-7942
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