Visualization of calcium dynamics in mouse neural circuits with epifluorescence mini microscopes and chronically
implanted lenses
Calcium Imaging; GCaMP; Miniscope
Neurons are electrically and chemically excitable, when excited enough, several ions quickly move across the membrane, causing a depolarization. Among these ions, Ca2+ is the only one that in addition to participating in action potential is also biologically active, participating in various cellular events, acting primarily as a cellular messenger. Studying the role of Ca2+ in the various events was possible through the development of techniques that allowed to measure its dynamics, such as the development of optical tools, being the first generation composed of dyes and later, with the advent of molecular engineering, the genetically encoded calcium indicators (GECIs), composed by hybridization of a fluorescent protein linked to a sensor protein. From early dyes to the most current GECIs, many advances have been made in increasing temporal and spatial resolution, Ca2+ sensitivity, photobleaching resistance, decreased phototoxicity, and high signal-to-noise ratio. However, in vivo mammalian preparations remained a challenge. Currently, GCaMP variants are one of the most commonly used GECIs, which are composed of calmodulin as a sensor protein, linked to a green fluorescent protein (GFP). In this work we will evaluate GCaMP expression with different viral promoters and calcium signals in vivo, in records made with adult mice walking in a treadmill at different speeds, using chronically implanted lenses and epifluorescence cameras.