Cerebral dopaminergic receptors
Postron emission tomography
Springer Online Journal Archives 1860-2000
Abstract A comparative evaluation of three radiobrominated butyrophenone neuroleptics — bromospiperone (BSP), brombenperidol (BBP), and bromperidol (BP) — was made to assess the applicability of these compounds as radiopharmaceuticals labelled with the positron emitter 75Br (T 1/2=1.6 h) for mapping cerebral dopaminergic receptor areas non-invasively with positron emission tomography (PET). BSP, BBP, and BP were prepared in high specific activities with high radiochemical yields, using electrophilic reactions with no-carrier-added 77Br- or 75Br-. Screening tests in rats using 77Br-labelled compounds indicated D2-specific localization for 77Br-BSP and 77Br-BBP, whereas PET experiments in baboons showed that only 75Br-BSP preferentially localized in cerebral tissues rich in dopaminergic receptors. The data suggest an inverse relationship between cerebral uptake and receptor-specific localization, which was attributed to a complicated interplay between the D2 receptor binding affinity, lipophilicity, % ionization and molecular weight of the radioligand, and the binding capacity of the cerebral tissues. 75Br-BSP gave a striatumto-cerebellum ratio of 3 in baboon brain 5 h post-injection, which allowed visualization of dopaminergic-receptor-containing areas of the living brain using PET.
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