54. A Model of a CA3 Hippocampal Neuron Incorporating Channelrhodopsin-2 Light Gated Ion Channels

Konstantin Nikolic1 k.nikolic@imperial.ac.uk Nir Grossman1,2 n.grossman@imperial.ac.uk Patrick Degenaar1,2 p.degenaar@imperial.ac.uk

1Institute of Biomedical Engineering, Imperial College, London, UK
2Division of Neuroscience, Imperial College, London, UK

The possibility of use of light sensitive proteins, such as channelrhodopsin-2 (ChR2), for the excitation of neurons is opening up a new field in neuroscience. The activation of genetically-encoded ChR2 molecules depolarizes neurons in response to blue light. These ion channels spontaneously close down after about ten milliseconds. In order to simulate the generation of action potentials in these cells we have developed a Matlab code based on the CA3 Hippocampal neuron models available in the open literature [Traub et.al. (1991), Migliore et.al. (1995)] and our models for the ChR2 photo-current kinetics [Nikolic et.al. (2008 )]. The results of simulations are compared with our experimental results. Very precise patters of action potentials can be created using this tool, however there is currently an upper limit of how fast the cells can be driven with this current, which is around 40Hz. Our model allows us to get a better insight into the dynamics of the action potentials generated by light and to identify possible improvements in the stimulation patters.

Migliore M., et.al. (1995), J. Neurophys. 73, 1157-1168
Traub R.D., et.al. (1991), J. Neurophys. 66, 635-650
Nikolic, K. et.al. (2008), submitted to Biophys. J.