A Protocol for Surgical Preparation of Rats for In Vivo Fiber Optic Photometry Using Genetically Encoded Fluorescent Biosensors

Genetically encoded biosensors based on fluorescent proteins in combination with fiber-optic neurointerface technology constitute a powerful tool for neurobiological research. Optical fibers can be implanted into the target brain regions of laboratory mammals, while the genetically encoded nature of biosensors enables in vivo monitoring of biochemical processes at the level of specific cell types and their compartments. As the global collection of biosensors for various biological parameters continues to expand, this approach is gaining increasing popularity. The ability to record fluorescent signals in real time, as well as at intervals over extended periods of several weeks or even months, makes the method broadly applicable for studying both acute and chronic processes in animal models of neurological disorders. Here, we describe in detail the protocol for preparing rats for fiber-photometry experiments using implantation of three optical fibers as an example. The protocol provides detailed instructions for the fabrication of universal optical probes that are compatible with both commercially available fiber-photometry systems and custom optical setups.