Dementia afflicts more than 55 million patients worldwide, and Alzheimer's disease (AD) accounts for around 60% to 80% of total cases 1 . During the onset of AD, the hippocampus (HC) is among the first-affected brain regions to experience pathological changes. Therefore, identifying changes to HC in AD subjects will be extremely helpful in providing early-stage diagnosis and interventions. We are developing in vivo techniques to investigate microscopic alterations to hippocampal structure and function in animal models of AD. Imaging will be performed using removable GRIN (gradient-index) lenses to chronically access subcortical brain structures with two-photon microscopy. Here, we report the development and characterization of a customized cannula (1 mm diameter, 6 -7 mm length) to repeatedly insert a GRIN lens for two-photon imaging. The cannula allows for easy removal of the lens after imaging sessions and enables detailed investigations of hippocampal changes during AD progression in mouse models. The cannula is made of polyimide tubing and tipped with transparent acrylic coverslip. We compare acrylic coverslips and existing glass coverslips in terms of physical and optical properties. Acrylic coverslips display comparable imaging quality and therefore serves as a reliable alternative to glass coverslips which is more economical, reproducible, and mechanically stable. We also present preliminary hippocampal images collected in vivo with our custom cannula. These results will guide more extensive efforts to measure hippocampal metabolic and hemodynamic alterations in awake animal models of AD.
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