A chronic scopolamine-induced animal model for cognitive alterations research-anatomy and metabolism

As long as complete etiology and curative treatment of Alzheimer's disease (AD) are not available, numerous an-imal species have been tested, but the ideal AD model has not been yet found. Although wild -type rodents do not develop beta amyloidplaques or neurofibrillary tangles, rat species present some advantages for anatomical and functional AD modeling. Material and meth-ods: Memory impairment was induced by intraperitoneal injection of 2 mg/kg scopolamine (Sco) into Wistar male rats. A control group received a similar injection with 0.2 mL physio-logical saline. Hybrid imaging acquisitions 18F-fluorodeoxyglucose PET/MRI (18F-FDG PET/MRI) were achieved after 14 days of administration and euthanasia for harvesting rat brains and cerebral samples preservation was accomplished after 28 consecutive days of treatment. Specific cerebral regions were visually evaluated and quantified using standard-ized uptake values, then were correlated with the anatomic regions harvested, comprising: the cerebral cortex, hippocampus, thalamus, and cerebellum, a separate sample being col-lected for each side. Results: In coronal view, 56 cerebral samples, 160 cerebral MRI, and over 800 18F-FDG PET cerebral images were obtained. Although anatomical macroscopic differences were not found between rats cerebral brains, in vivo functional imaging provided an obvious distinction between the saline-treated and the Sco-induced animals, changes that persist in long-term administration. Conclusions: The present study proves that the cerebral metabolism increase is maintained during chronic administration of Sco, with intense metab-olism in the amygdala, the entorhinal cortex, and other specific cerebral regions specialized in memory processing. We emphasize the functional impact of Sco-induction correlated with anatomical implications after tissue dissection.