Imaging brain activity: Longitudinal fMRI in mice using medetomidine sedation

Introduction: Functional MRI (fMRI) using the endogenous blood oxygenation level-dependent (BOLD) contrast is a widely used technique to study brain activity non-invasively. It is the method of choice to assess damage and recovery processes in animal models of brain injury. In mice, fMRI has been performed under α-chloralose [1] or pure isoflurane [2]. Both approaches are unsuitable for longitudinal fMRI experiments due to severe side effects or the need of strong electrical stimulation, resulting in pain dependent brain activation. In rats, longitudinal fMRI has been successfully performed using the sedative drug medetomidine [3]. Here, we present the first longitudinal fMRI protocol for mice, which allows repetitive and non-invasive fMRI experiments in the somatosensory cortex of mice.