Functional changes in the basal ganglia-thalamus-cortex loop in L-DOPA-induced dyskinesia in a mouse model of unilateral Parkinson's disease

Advances in MRI imaging techniques such as diffusion tensor imaging and functional magnetic resonance imaging (fMRI) make it possible to noninvasively measure the structure of cerebral white matter fibers and neural activity in the brain. Clinical application of these techniques is expected for early diagnosis of Parkinson's disease and evaluation of pathophysiology and treatment efficacy. In this study, we used MRI to examine changes in functional connectivity in [JAG1] mice in which 6-hydroxydopamine (6-OHDA) was unilaterally injected into the medial forebrain bundle of the mouse and which displayed L-DOPA-induced dyskinesia. Resting-state fMRI was measured under light anesthesia before and after administration of L-DOPA (XX mg/kg), which induces dyskinesia. Before L-DOPA, the interhemispheric functional connectivity within basal ganglia-thalamo-cortical loops was significantly decreased in lesioned mice compared with sham-operated mice. In contrast, L-DOPA administration increased functional connectivity in the intra/interhemispheric basal ganglia-thalamo-cortical loops in lesioned mice, but not in sham mice.[DH2] These results indicate that functional connectivity in interhemispheric basal ganglia-thalamo-cortical loops is decreased in the absence of dopamine but restored by L-DOPA.