Optogenetic Stimulation of Neurons in the Brainstem of Freely Behaving Rats and Mice

Optogenetics is the combination of genetic and optical methods to achieve gain or loss of function of well-defined events in specific cells in living tissues. One of the strengths of this approach is that it can be used in conscious animals without impeding normal behavior. This method has been implemented to interrogate the neural determinants of behaviors including feeding, breathing, aggression, and arousal. Here I describe the procedures for stereotaxically guided delivery of opsin-encoding virus in deep brainstem structures of rodents, the implantation of guide cannulas and optical fibers to photostimulate neurons in vivo. The expected results and caveats are discussed.