Shallow-angle intracranial cannula for repeated infusion and in vivo imaging with multiphoton microscopy.

Significance: Multiphoton microscopy serves as an essential tool for high-resolution imaging of the living mouse brain. To facilitate optical access to the brain during imaging, cranial window surgery is commonly used. However, this procedure restricts physical access above the imaging area and hinders the direct delivery of imaging agents and chemical compounds to the brain.

Aim: We aim to develop a method that allows the repeated administration of imaging agents and compounds to the mouse brain while performing in vivo imaging with multiphoton microscopy.

Approach: We have developed a cannula delivery system that enables the implantation of a low-profile cannula nearly parallel to the brain surface at angles as shallow as 8 deg while maintaining compatibility with multiphoton microscopy.

Results: To validate our shallow-angle cannula approach, we performed direct infusion and imaging of various fluorescent cell markers in the brain. In addition, we successfully demonstrated tracking of degenerating neurons over time in Alzheimer's disease mice using Fluoro-Jade C. Furthermore, we showed longitudinal imaging of the partial pressure of oxygen in brain tissue using a phosphorescent oxygen sensor.

Conclusions: Our developed technique should enable a wide range of longitudinal imaging studies in the mouse brain.