Synthesis and Biodistribution of ~(131)I-MPPI as 5-HT_(1A) Imaging Agent

The synthesis and biological evaluation of serotonin(5HT_(1A)) imaging agent _4-iodo-N-_1-piperazinyl]ethyl-N-2-pridinyl-benzami-de(~(131)I-MPPI)were reported.The chemical structure of aimed compound and intermediates were confirmed by IR,~(1)H NMR and MS.Radiochemical purity is above 99% determined by TLC.Biodistribution of ~(131)I-MPPI in rats displayed high uptake in hippocampus and low uptake in cerebellum.The ratio of the uptake of ~(131)I-MPPI in hippocampus to cerebellum is 2.90 at(30 min) post-injection.Autoradiography of brain section displayed significant decrease of radioactivity in hippocampus when rats were pretreated with 8-OH-DPAT,a selective 5-HT_(1A) agonist,compared with control.The uptake ratios of thyroid are(0.069±0.020)% and((0.128±)0.026)% at 5 min and 120 min,respectively,and they are increased with time,suggesting that in vivo deiodination may be the major route of metabolism.These findings strongly suggested that ~(131)I-MPPI could be used as an in vivo marker for studies of the pharmacology of the 5-HT_(1A) receptor system in animal.