Neuron

Neuron

Volume 11, Issue 5, November 1993, Pages 845-855
Journal home page for Neuron

Article
Ca2+ is an obligatory intermediate in the excitation cascade of limulus photoreceptors

https://doi.org/10.1016/0896-6273(93)90114-7Get rights and content

Abstract

We have investigated the role of Ca2+ in the excitation of Limulus photoreceptors by intracellular injection of the Ca2+ buffer, 5,5′-dibromo-BAPTA. Buffer with free Ca2+ of 0.5 or 5 μM slowed the rising edge of the light response over 100-fold and greatly reduced both the transient and plateau phases of the light response, as expected if Ca2+ elevation is necessary for all phases of excitation. Injection of buffers with free Ca2+ of 5 or 45 μM, levels normally reached during light, evoked sustained inward current as expected if Ca2+ is sufficient for excitation. The transduction cascade appears due to a single pathway that sequentially involves 1,4,5-trisphosphate inositol, Ca2+, and cyclic GMP.

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