Kinetic evaluation of photosensitivity in genetically engineered neurons expressing green algae light-gated channels

Neurosci Res. 2006 Feb;54(2):85-94. doi: 10.1016/j.neures.2005.10.009. Epub 2005 Nov 17.


Neurons become photosensitive by genetically introducing one of green algae-derived protein, channelrhodopsin-2 (ChR2). Here, we quantitatively investigated the rapidness of the light-gated current of ChR2 expressed in PC12 cells using blue light-emitting diode (LED) light. The light-gated current consists of two components, inactivating and non-inactivating. The magnitude of inactivating component was almost linearly related to the light intensity. The non-inactivating component showed a tendency to saturate at high illumination. Both the activation and inactivation rates of the light-gated current were linearly dependent on the light intensity. However, the activation rate (turning-on rate) is about 10-fold faster than the inactivation rate. Although the turning-off time constant was little dependent on the light intensity, that at the end of 1s light pulse was about two-fold larger than that at 20 ms. Neurons are also made photosensitive by the expression of ChR2 in the living animal. Since both the turning-on and turning-off time constants of light-gated current was smaller than the membrane time constant of neurons, the LED light illumination of the photosensitive neurons was enough to evoke action potentials in a pulse-to-pulse manner in an acute slice of hippocampus.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Algorithms
  • Animals
  • Chlorophyta / metabolism*
  • DNA, Complementary / biosynthesis
  • DNA, Complementary / genetics
  • Genetic Engineering*
  • Hippocampus / cytology
  • Ion Channel Gating / physiology*
  • Ion Channel Gating / radiation effects
  • Ion Channels / biosynthesis
  • Ion Channels / genetics*
  • Ion Channels / radiation effects
  • Kinetics
  • Light
  • Membrane Potentials / physiology
  • Neurons / physiology*
  • Neurons / radiation effects*
  • PC12 Cells
  • Patch-Clamp Techniques
  • Photic Stimulation
  • Photochemistry
  • Rats
  • Rhodopsin / metabolism
  • Sindbis Virus / genetics
  • Transfection


  • DNA, Complementary
  • Ion Channels
  • Rhodopsin