Functional MRI (fMRI) was used to study striatal sensitivity to levodopa in hemiparkinsonian rhesus monkeys. Responses consistent with increased neuronal activity were seen in areas whose normal dopaminergic input from the substantia nigra pars compacta had been ablated by MPTP. Sites of increased activity following levodopa included the lateral putamen, the ventral region of the caudate head, septal areas, and midlateral amygdala in the MPTP- lesioned hemisphere. Increased activity was also observed in the same areas in the nonlesioned hemisphere, but was less pronounced in spatial extent and magnitude, suggesting either subclinical contralateral damage and/or functional adaptations in the contralateral dopamine systems. The increases in neuronal activity following levodopa treatment were temporally correlated with increases in striatal dopamine levels. Chronic levodopa treatment reduced behavioral responsiveness to levodopa and abolished the fMRI response. These results suggest that fMRI can detect changes in dopamine receptor-mediated neuronal sensitivity to dopaminergic agents.
|Number of pages||13|
|State||Published - Jul 1999|
Bibliographical noteFunding Information:
We thank Dr. Greg Gerhardt and the Rocky Mountain Center for Sensor Technology for supplying the microdialysis probes used in this study. This work was supported by NIH Grants NS35080 (M.J.A.) and NS25778 (D.M.G.) and by the Vice Chancellor for Research and Graduate Studies, University of Kentucky Medical Center.
ASJC Scopus subject areas
- Developmental Neuroscience