Modulation of the light response by cAMP in Drosophila photoreceptors

Sylwester Chyb, Wulf Hevers, Michael Forte, William J. Wolfgang, Zvi Selinger, Roger C. Hardie

Research output: Contribution to journalArticlepeer-review

62 Scopus citations


Phototransduction in Drosophila is mediated by a G-protein-coupled phospholipase C transduction cascade in which each absorbed photon generates a discrete electrical event, the quantum bump. In whole-cell voltage-clamp recordings, cAMP, as well as its nonhydrolyzable and membrane-permeant analogs 8-bromo-cAMP (8-Br-cAMP) and dibutyryl-cAMp, slowed down the macroscopic light response by increasing quantum bump latency, without changes in bump amplitude or duration. In contrast, cGMP or 8-Br-cGMP had no effect on light response amplitude or kinetics. None of the cyclic nucleotides activated any channels in the plasma membrane. The effects of cAMP were mimicked by application of the non-specific phosphodiesterase inhibitor IBMX and the adenylyl cyclase activator forskolin; zaprinast, a specific cGMP-phosphodiesterase inhibitor, was ineffective. Bump latency was also increased by targeted expression of either an activated G(s) α subunit, which increased endogenous adenylyl cyclase activity, or an activated catalytic protein kinase A (PKA) subunit. The action of IBMX was blocked by pretreatment with the PKA inhibitor H-89. The effects of cAMP were abolished in mutants of the ninaC gene, suggesting this nonconventional myosin as a possible target for PKA-mediated phosphorylation. Dopamine (10 μM) and octopamine (100 μM) mimicked the effects of cAMP. These results indicate the existence of a G-protein-coupled adenylyl cyclase pathway in Drosophila photoreceptors, which modulates the phospholipase C-based phototransduction cascade.

Original languageEnglish (US)
Pages (from-to)8799-8807
Number of pages9
JournalJournal of Neuroscience
Issue number20
StatePublished - Oct 15 1999
Externally publishedYes


  • Adenylyl cyclase
  • Calcium
  • Cross- talk
  • Dopamine
  • Neuromodulation
  • Phospholipase C
  • Photoreceptor
  • Phototransduction
  • TRP

ASJC Scopus subject areas

  • Neuroscience(all)


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