Delivery of AAV for Expression of Fluorescent Biosensors in Juvenile Mouse Hippocampus

Genetically encoded fluorescent biosensors are versatile tools for studying brain metabolism and function in live tissue. The genetic information for these biosensors can be delivered into the brain by stereotaxic injection of engineered adeno-associated viruses (AAVs), which can selectively target different cell types depending on the capsid serotype and/or the viral promoter. Here, we describe a protocol for intracranial injections of two viral vectors encoding the metabolic biosensor Peredox and the calcium biosensor RCaMP1h. When combined with 2-photon microscopy and fluorescence lifetime imaging, this protocol allows the simultaneous quantitative assessment of changes in the cytosolic NADH/NAD⁺ ratio and the intracellular Ca²⁺ levels in individual dentate granule cells from acute hippocampal slices. Graphic abstract: Workflow diagram for biosensor expression in the mouse hippocampus using intracranial injections of adeno-associated viruses.