STRUCTURE BIODISTRIBUTION RELATIONSHIP OF RADIOIODINATED TROPEINES - SEARCH FOR A MOLECULAR PROBE FOR THE CHARACTERIZATION OF THE COCAINE RECEPTOR

Three iodinated analogs of cocaine were synthesized and radiolabeled by isotope exchange in the presence of Cu++ using a “kit” procedure. 2′‐Iodococaine,2′‐iodotropacocaine and 2′‐iodobenzoyl tropine radiolabeled with 125I were injected in mice and their biodistribution studied. Activity with all three radiolabeled compounds peaked in the brain and heart between 5 and 30 min. post injection. Activity from 125I‐2′‐iodococaine (S.A.=468 mCi/mmol), peaked in the brain at 15 min (2.38% injected dose/g) and showed a plateau in the heart between 5 and 60 min post injection (1.67–2.16%). 125I‐2′‐iodotropacocaine (S.A.=407 mCi/mmol) at 5 min had the highest uptake in the brain (8.16%) and the heart (4.44%) while activity from 125I‐2′‐iodobenzoyl tropine (S.A.=407 mCi/mmol) peaked in the brain at 15 min (4.19%) and at 5 min in the heart (3.33%). The biodistribution of 125I‐2′‐iodococaine paralleled literature values obtained with 3H‐/14C‐cocaine. We conclude that radioiodinated tropeines radiolabeled with 123I may be developed into useful probes to examine and characterize the cocaine receptor in‐vivo by SPECT imaging. Copyright © 1990 John Wiley & Sons, Ltd.