Optogenetics has recently revolutionized the field of neuroscience. The technique involves the delivery of light- sensitive ion channels or pumps (opsins) to genetically defined subpopulations of neurons in the brain. Upon illumination with the appropriate wavelength of light, membrane localized opsins become activated and either depolarize or hyperpolarize (depending on the type of opsin) the membrane potential of neurons expressing them. Thus, optogenetics offers an unparalleled means of controlling neural activity in a temporally and spatially precise manner. Not only does optogenetics have broad implications as a research tool for studying complex neural networks, but it also shows great potential to be used directly as a treatment for diseases like epilepsy. Indeed, the optogenetic approach has been recently used to halt seizure activity in various animal models. However, despite the progress made towards a future clinical application, the use of optogenetic techniques in vivo still faces many important challenges that need to be addressed. Most of these challenges lie with the light source, which currently relies on using lasers or LEDs coupled to optical fibers implanted into the brain. Not only are these light sources impractical to use in long term in vivo settings (i.e. hardware dependency, limited tissue penetrance), they also pose a significant safety risk (e.g. heat-induced injury). The overall goal of this project is to addres the current technical limitations of using optogenetics in vivo by developing bioluminescent proteins as an alternative light source for activating light-sensitive opsins. The proposed research will develop several optogenetic systems using bioluminescent proteins. In the first aim, we will show that luciferases can be used to activate opsins in vitro. In the second aim, we will tie bioluminescence to neural activity in order to create novel optogenetic feedback systems. These systems will then be studied in the context of controlling epileptic activity in acute brain slices. The proposed research would therefore not only provide an alternative means to activate opsins (adding to the robustness of the tool for neuroscience research), but would also provide a novel approach to controlling seizure activity seen in epilepsy.