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 language||English (US)|
|Number of pages||6|
|Journal||Proceedings of the National Academy of Sciences of the United States of America|
|State||Published - Sep 1 2009|
All Science Journal Classification (ASJC) codes
- Laser-scanning microscopy