Manganese enhanced MRI in rat hippocampus: A correlative study with synchrotron X-ray microprobe

Manganese enhanced MRI (MEMRI) offers many possibilities such as tract tracing and functional imaging in vivo. Mn is however neurotoxic and may induce symptoms similar to those associated with Parkinson's disease (manganism). The mechanisms of Mn-induced neurotoxicity are not clear. In this study, we combine synchrotron X-ray fluorescence microprobe (SR-XRF) and MEMRI techniques to investigate spatial distribution of Mn within the rat hippocampus and how Mn interacts with Ca, Fe and Zn at a cellular level. Images were acquired in the rat hippocampus (n=23) and using two injection routes: intra-cerebral (MnCl2: 50mM, 10μL) and intra-peritoneal (MnCl2: 100mM, 30mg/kg). For both injection routes, Mn is found in dentate gyrus and in CA3: control: 2.5±1.6, intra-peritoneal: 5.0±2.4, and intra-cerebral: 25.1±9.2μg/g. Mn follows Zn distribution and has a negative impact on the total amount of Zn and Fe. The Mn-enhanced MRI contrast is well correlated with the total Mn amount measured with SR-XRF (R2=0.93; p