ABSTRACT
Objective To evaluate the feasibility of 3-(4-~(18)F-fluorobenzyl)-8,9-dimethoxy-1,2,3,4-tetrahydrochromeno [3,4-c]pyridin-5-one ( is F-FDTP) as a potential dopamine D4 receptor PET imaging agent.Methods ~(18)F-FDTP solution in ethanol-physiological saline was incubated with calf serum to test its in vitro stability through the determination of radiochemical purity.Normal rats were injected intravenously with ~(18)F-FDTP and then sacrificed at 2,5,10,15,30,60 and 120 min after anesthesia.Blood,organs and brain tissue samples were collected.All samples were weighed and measured for radioactivity.The uptake of samples was expressed as percentage activity of injection dose per gram of tissue ( % ID/g).Results The stability of ~(18)F-FDTP was satisfactory and its radiochemical purity was above 95% after incubation 120 min at 37℃ in calf serum.The biodistribution showed that ~(18)F-FDTP could penetrate through the blood-brain barrier and selectively accumulate in striatum,hypothalamus,frontal certex,hippocampus,cerebellum,where the D_4 receptor was reportedly located.The radioactivities in hippocampus,hypothalamus,striatum,frontal cortex,cerebellum,pons were (0.42±0.03),(0.46±0.05),(0.54±0.04),(0.39±0.04),(0.45±0.06),(0.35±0.04) %ID/g,respectively,2 min post injection.And there was difference between the normal biodistribution results and the blocking experimental results:(0.36 ±0.05),( 0.33±0.05 ),(0.55±0.05 ),(0.30±0.07 ),(0.34±0.07 ) and (0.32±0.04) % ID/g in hippocampus,hypothalamus,striatum,frontal cortex,cerebellum and pons,respectively.Conclusions ~(18)F-FDTP can penetrate through the blood-brain barrier and selectively accumulate in striatum,hypothalamus,frontal cortex,hippocampus,cerebellum,where the D_4 receptor was known to concentrate.These preliminary results suggest that ~(18)F-FDTP is a potential dopamine D_4 receptor imaging agent and further studies are needed.