Midbrain viral injections for striatal fiber photometry in mice

This protocol describes how to: - Inject AAV viruses into the midbrain (SNc: substantia nigra pars compacta, or VTA: ventral tegmental area) of mice - Train mice for head-fixed running on a cylindrical treadmill, and to receive rewards and air puffs while head-fixed - Implant head plates on mice for head-fixation during behavior (optional) While this protocol is focused on injections of AAV viruses into the midbrain, it can be easily modified to inject into other brain regions or other viruses.