Manganese-enhanced MRI in a rat model of Parkinson's disease

Purpose: To measure intra- and inter-hemispheric connectivity within the basal ganglia (BG) nuclei in healthy and in unilateral 6-hydroxydopamine (6-OHDA) Parkinson disease rat model in order to test the BG interhemispheric connectivity hypothesis. Material and Methods: The manganese-enhanced MRI (MEMRI) method with direct injection of manganese chloride into the entopeduncular (EP), substantia nigra (SN), and the Habenula nuclei in unilateral 6-OHDA (N = 22) and sham-operated (N = 16) rat groups was used. MEMRI measurements were applied before, 3, 24, and 48 hours post-manganese injection. Signal enhancements in T1-weighted images were compared between groups. Results: Manganese injection into the EP nucleus resulted with bihemispheric signal enhancements in the habenular complex (Hab) at both groups with stronger enhancements in the 6-OHDA group. It also exhibited lower sensorimotor cortex signal enhancement in the 6-OHDA rat group. SN manganese injection caused enhanced anteroventral thalamic and habenular nuclei signals in the 6-OHDA rat group. Manganese habenula injection revealed enhanced interpeduncular (IP) and raphe nuclei signals of the 6-OHDA rat group. Conclusion: Modulations in the effective intra- and interhemispheric BG connectivity in unilateral 6-OHDA Parkinson's disease (PD) rat model support the BG interhemispheric connectivity hypothesis and suggest a linkage between the dopaminergic and serotonergic systems in PD, in line with clinical symptoms.