Manganese (Mn²⁺) is a paramagnetic MRI contrast agent. It enters neurons by calcium channels and is transported along the axons anterogradely. In this manner, manganese enhanced magnetic resonance imaging (MEMRI) can be used to directly map the neurons activated by nicotine. As neuronal activation can be measured by MEMRI, this approach appears as a powerful first step analyses for nicotine addiction and withdrawal.

Signal alteration on nucleus accumbens (ACB) and hippocampus (HIP) in controls (PBS injected rats) and nicotine injected rats. A. Signal increase on ACB with time (*: P < 0.05). The MR image (right) illustrates the anatomy of ACB (enclosed by a red line). B. Signal increase on HIP with time (*: P < 0.05). MR image (right) illustrates the anatomy of HIP (enclosed by a red line).

MRI enhancement maps of controls and rats with chronic nicotine exposure. A. The first row represents coronal slices of the averaged MEMRI of control rats as an anatomical reference. The sagittal slice (upper left)  shows respective coronal positions (red lines). B. MRI enhancement map of controls. C. Enhancement map of rats with chronic nicotine exposure. The pseudo-colors of the enhancement maps are demonstrated using a color bar (at the top of figure).

For further information, see:  Bade AN, Gendelman HE, Boska MD, Liu Y. MEMRI is a biomarker defining nicotine-specific neuronal responses in subregions of the rodent brain. Am J Transl Res. 2017 Feb 15;9(2):601-610.