Long-term two-photon transcranial imaging of synaptic structures in the living brain.

INTRODUCTIONThis is a detailed protocol for long-term transcranial imaging of neuronal structures in the brains of living mice, using two-photon microscopy. It has been used to image individual dendritic spines and axonal varicosities in various mouse brain areas, such as visual, somatosensory, motor, and frontal cortices, over intervals of up to 4 months. This long-term transcranial imaging approach allows detailed structural and functional changes of synapses to be monitored during learning and memory processes, as well as in neurological disease models. It also provides a sensitive tool to detect the effects of various pharmacological and therapeutic interventions on cells in the living brain.