Protocol for fiber photometry recording from deep brain regions in head-fixed mice

To exclude the influence of motion on in vivo calcium imaging, animals usually need to be fixed. However, the whole-body restraint can cause stress in animals, affecting experimental results. In addition, some brain regions are prone to bleeding during surgery, which lowers the success rate of calcium imaging. Here, we present a protocol for calcium imaging using heparin-treated fiber in head-fixed mice. We describe steps for stereotaxic surgery, including virus injection and optic fiber implantation, fiber photometry, and data analysis. For complete details on the use and execution of this protocol, please refer to Du et al.1