Two-photon excitation of channelrhodopsin-2 at saturation

John Peter Rickgauer, David W. Tank

Research output: Contribution to journalArticlepeer-review

229 Scopus citations


We demonstrate that channelrhodopsin-2 (CR), a light-gated ion channel that is conventionally activated by using visible-light excitation, can also be activated by using IR two-photon excitation (TPE). An empirical estimate of CR's two-photon absorption crosssection at λ = 920 nm is presented, with a value (260 ± 20 GM) indicating that TPE stimulation of CR photocurrents is not typically limited by intrinsic molecular excitability [1 GM = 10 -50(cm4 s)/photon]. By using direct physiological measurements of CR photocurrents and a model of ground-state depletion, we evaluate how saturation of CR's current-conducting state influences the spatial resolution of focused TPE photostimulation, and how photocurrents stimulated by using low-power scanning TPE temporally summate. We show that TPE, like visible-light excitation, can be used to stimulate action potentials in cultured CR-expressing neurons.

Original languageEnglish (US)
Pages (from-to)15025-15030
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number35
StatePublished - Sep 1 2009

All Science Journal Classification (ASJC) codes

  • General


  • Laser-scanning microscopy
  • Optogenetics
  • Photostimulation


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