Visualização da dinâmica de cálcio em circuitos neurais de camundongos com mini microscópios de epifluorescência e lentes cronicamente implantadas

Abstract

All cognitive processes are originated from the response of neuronal populations. However, while recording methods for one or few cells have been used for decades, the study of large neuronal populations, with cell type specificity, is still complex. The evolution in imaging methods and functional staining has allowed the 'visualization' of the activity of neuronal populations, when these methods are combined with techniques of gene manipulation, functional imaging allows the activity of genetically specific populations to be recorded. GCaMP has been the most widely used family of genetically encoded activity indicators, from the visualization of Ca2+ dynamics, in mammalian preparations in vivo. However, for the relationship between the activity of neuronal populations and behavior to be established, the Ca2+ imaging method must allow the animal to be able to exercise freely. To measure variations in fluorescence, mini epi-illumination microscopes (known as Miniscope) are mounted above the animals' heads, their size and reduced weight allow free movement. These Miniscopes are produced by the user's laboratory, or by third parties, and use mass production components that are cheap and easy to find. However, calcium imaging experiments that involve miniscopes require testing with different strains of animals and viral constructs, understanding the variation in their dynamics, surgical standardization and improving the recording systems. This dissertation explores the previous points and as proof of principle the Ca2+ imaging is performed in the hippocampus of animals while they run on a treadmill in the presence of loud broadband sounds. The analysis of the series of images containing neuronal activity is also briefly discussed.