Protocol for sparse labeling of murine Purkinje cells by intracerebroventricular AAV injection using a microelectrode holder

Most microinjection techniques require expensive machinery and can be difficult to perform consistently. Here, we present a protocol for long-term, stable gene delivery by adeno-associated virus (AAV) vectors through intracerebroventricular injection of neonatal mice using a microelectrode holder equipped with borosilicate needles. We describe steps for building the device, pulling the needles, preparing and injecting the neonates, tissue perfusion and collection, and sample preparation. We then detail procedures for immunofluorescent antibody staining and imaging, followed by image reconstruction, export, and analysis.