Distribution of Dopamine D2 Receptor PET Imaging Agent 18F-Fallypride in the Brain of Normal and Aged Rats

With the progress of population aging, the incidence of agerelated disease has greatly increased. The dopamine D2 receptor is closely related to the age-related diseases, such as PD and AD. The PET imaging of the dopamine D2 receptor can provide noninvasive, dynamic, early and quantitative information on the function of the brain. So we intend to prepare dopamine D2 receptor PET imaging agent ¹⁸F-Fallypride and to study the disturbution of the agent in the brain of normal and aged rats, further to explore the relationship between dopamine D2 receptor and senility. ¹⁸F-Fallypride was prepared by nucleophilic reaction. And the PET image was performed in aged and normal rats 15 minutes after injection of the agent.Striatums were delineated as the region of interesting (ROI), the standard uptake value (SUV) of which was calculated. PMOD was used for image fusion, partition and quantitative analysis of standard uptake values of each brain area. After imaging, cardiac ventricle was perfused. The brain was obtained and frozen. The contour structure was observed by HE staining.The results showed that the labeling yield was over 95% and the radiochemical purity was higher than 98%. The stability was still over 95% 2 hours after incubation with PBS. The striatum uptake of ¹⁸F-Fallypride radioactivity in aged and normal rats 15 minutes after injection were (0.58±0.11)%ID/g, (0.39±0.14)%ID/g. The uptake of cortex cingulate, cortex insular, hypothalamus, olfactory, midbrain in normal rats ((0.120±0.012)%ID/g, (0.182±0.002)%ID/g, (0.111±0.002)%ID/g, (0.127±0.007)%ID/g, (0.083±0.012)%ID/g respectively) were inferior to aged rats ((0.154±0.013)%ID/g, （0.344±0.014）%ID/g, （0.244±0.019）%ID/g, （0.263±0.020）%ID/g, （0.216±0.012）%ID/g), which was displayed by PMOD. HE staining showed severe brain injury in elderly SD rats. Some neurons in the aged SD rats appeared acidophil change or nuclear fragmentation, accompanied by spongy deformation, lamellar or focal neuronal necrosis, and no obvious morphological changes. The relevance between dopamine D2 receptor and senility was demonstrated by PET imaging, which provided a basis for further research on the methodology of disease and pharmacodynamics research.