The protocol for mesoscopic wide-field optical imaging in mice: from zero to hero
This article provides protocols that make possible to master mesoscopic wide-field optical brain imaging from scratch. The protocols describe surgery for wide-field cranial window creation in mice, and wide-field imaging process and setup. The protocols for components of imaging system selection and assembly, creation of a headplate for fixation, and mice training are also provided. The last part briefly describes methods for data processing. The above procedure can be used to visualize dorsal cortex via wide-field optical imaging as well as laser-speckle contrast imaging methods. The distinguishing features of our protocol are: a wide cranial window (up to 60% of the entire cortex), scull thinning (without craniotomy), ultraviolet-curable transparent coating (gel polish), measurements in awake behaving mice. During the surgery the helicopter-like headplate with its lower surface congruent to scull surface is mounted on mouse head. This headplate is lightweight and enable to fix head securely during movement to avoid frames alignment during data processing. Cranial window remains sufficiently transparent for at least 3 months. Wide-field optical imaging method enables to record brain haemodynamics and energy metabolism (FAD concentration dynamics) in wild-type mice. Use of transgenic animals expressing genetically-encoded sensors enable measurements of ions concentration (e.g. Ca2+-dynamics) and other compounds (e.g. glutamate). The article describes measurements by wide-field optical imaging of oxy-, deoxy-, and total haemoglobin concentrations changes in combination with various intracellular parameters: {Delta}[FAD] or {Delta}[Ca2+] or {Delta}pH with {Delta}[Cl-].