Airan and colleagues describe the work that they have done to genetically couple optic receptors to g-proteins (like cAMP) inside neuronal molecules. After developing the coupled receptor, they first show that their technique can recruit the same amount of cAMP after 60 seconds of exposure to light as the cell emits after 5 minute exposure to 10 microM of noepinephrine. Their other coupled receptor recruits the same amount of inositol trisphosphate after 60 seconds of light exposure than the similarly compatible type of noepinpephine exposure. So basically they engineered a way to control the stimulation of individual neurons in two pathways via the differential elevation of light.
After showing that their optogenetic approach can work to stimulate mice neurons in vivo, the researchers go on to show that it can modulate behavior in a learning paradigm. By optically controlling neurons in the nucleus accumbens with a 473 nm laser diode inserted in the brain, they caused mice to show a significant preference to move into one chamber over another as compared to control mice. In order to accomplish this, they delivered a laser-diode-coupled optical fibre to the accumbens with light pulses at 10 Hz, simulating the monoaminergic input that would likely follow a strong reward. This is a powerful new method for learning and behavior research and hopefully the technique and its probable iterations (like a wireless approach) will soon become widespread.
Airan DG, et al. 2009 Temporally precise in vivo control of intracellular signalling. Nature, doi:10.1038/nature07926.