Radioiodinated 1-substituted-4-phenylpiperazines as potential brain imaging agents.

A series of four 125I-labeled 1-substituted-4-phenylpiperazines were prepared and evaluated in rats as potential brain imaging agents. The compounds were labeled using [125I]iodide/chloramine-T or iodine monochloride and isolated in 48-60% radiochemical yields. The tissue distribution studies indicated that a butyrophenone derivative demonstrated the best overall brain-imaging properties. Compared with the compounds having other 1-substituents this agent had a more prolonged retention of activity in the brain and higher brain-to-blood ratios over the 4-h period studied. The in vivo behavior of this agent is comparable to that of radioiodinated N-isopropyl-p-iodoamphetamine, and, because it can be labeled directly via electrophilic methods, it has substantial potential for use in brain imaging with single photon emission computed tomography.