A Correlation Study of Early Cognitive Impairment in a Parkinson's Disease Rat Model Obtained with 2.35 T MRI and TH+ Immunoreactivity

"Early stage of PD lies on the unbalanced capability to manage self-paced versus externally driven movements, or automatic-. associated movement with respect to the intended voluntary movement. Several MRI studies found that non-demented. patients with PD had a significant rate of median\/global brain volume loss, and these changes correlated with global measures. of cognitive decline (1-3) strengthening the idea that both striatal DA depletion and regional or global brain volume loss. contribute to cognitive decline in PD (4).. Here, we examined the effect of an unilateral DA depletion of the right striatum, on the switching of a well learned task, as. revealed using tyrosine hydroxylase (TH) immunoreactivity and high-resolution 2.35T MRI in a rat PD model.. METHODS AND RESULTS. Male albino Wistar rats (n=18) were used. After completion of behavioural performances, the fixated whole brains. were scanned with a 2.35T Biospec equipped with a TX-only volume coil and a RX-only surface coil. GEFI images. (TR=3000ms; TE=40ms; FOV=1.5cm2; 256*256; slice thickness=1.1mm; NEX=18; TAQ=3h15min) were acquired covering. the whole brain. Coronal sections containing the striatum and substantia nigra were processed with cresyl violet and TH. immunohistochemistry.. The switching imposed after habit condition evidenced an interference action of EC cerebello-cortical circuitry upon the. ID striatal-cortical circuit building that became exclusive with DA depletion of the striatal-cortical circuitry. We found a. correspondence between visual evaluation of brain MRI scans, used as volumetric measurement in evaluating regional brain. atrophy and the histological section, showing a lesion localized in the striatum with an evident shrinkage of the whole striatum. and an enlargement of the ipsilateral ventricle. The nearly complete loss of TH+ immunoreactivity in the right striatum,. corresponded to a significant retrograde dopaminergic denervation in the ipsilateral substantia nigra."