MAPT and tauopathy: <h4>Background</h4>Repurposing dantrolene as a potential disease-modifying treatment for Alzheimer's disease has been shown to be effective in amyloid transgenic mouse models but has not been examined in a model of tauopathy.<h4>Objective</h4>The effects of a nanoparticle intranasal formulation, the Eagle Research Formulation of Ryanodex (ERFR), in young adult and aged wild type and PS19 tau transgenic mice was investigated.<h4>Methods</h4>The bioavailability of intranasal ERFR was measured in 2 months and 9-12 month old C57BL/6J male mice.