The phototransduction machinery in the rod outer segment has a strong efficacy gradient

Monica Mazzolini, Giuseppe Facchetti, Laura Andolfi, Remo Proietti Zaccaria, Salvatore Tuccio, Johannes Treud, Claudio Altafini, Enzo M. Di Fabrizio, Marco Lazzarino, Gert Rapp, Vincent Torre

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20 Scopus citations


Rod photoreceptors consist of an outer segment (OS) and an inner segment. Inside the OS a biochemical machinery transforms the rhodopsin photoisomerization into electrical signal. This machinery has been treated as and is thought to be homogenous with marginal inhomogeneities. To verify this assumption, we developed a methodology based on special tapered optical fibers (TOFs) to deliver highly localized light stimulations. By using these TOFs, specific regions of the rod OS could be stimulated with spots of light highly confined in space. As the TOF is moved from the OS base toward its tip, the amplitude of saturating and single photon responses decreases, demonstrating that the efficacy of the transduction machinery is not uniform and is 5-10 times higher at the base than at the tip. This gradient of efficacy of the transduction machinery is attributed to a progressive depletion of the phosphodiesterase along the rod OS. Moreover we demonstrate that, using restricted spots of light, the duration of the photoresponse along the OS does not increase linearly with the light intensity as with diffuse light. © 2015, National Academy of Sciences. All rights reserved.
Original languageEnglish (US)
Pages (from-to)E2715-E2724
Number of pages1
JournalProceedings of the National Academy of Sciences
Issue number20
StatePublished - May 4 2015

Bibliographical note

KAUST Repository Item: Exported on 2020-10-01
Acknowledgements: We thank Profs. Trevor Lamb and Fabio Benfenati for reading the manuscript, M. Lough for checking the English, and Paolo Fabris for MatLab support. This work was supported by FOCUS Contract 270483 (FP7-ICT-2009-6) from the European Union.

ASJC Scopus subject areas

  • General


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