Stereoselective binding of 11C-raclopride in living human brain--a search for extrastriatal central D2-dopamine receptors by PET

Psychopharmacology (Berl). 1988;94(4):471-8. doi: 10.1007/BF00212840.


The selective D2-dopamine receptor antagonist raclopride and its pharmacologically inactive (R)-enantiomer FLB472 were labelled with 11C and used in a study with positron emission tomography to examine the stereoselectivity of 11C-raclopride binding to central D2-dopamine receptors in three healthy men. After the injection of 11C-raclopride, there was a high accumulation of radioactivity in the dopamine-rich basal ganglia, whereas after the injection of 11C-FLB472 there was no such accumulation of radioactivity. Thus, the binding of 11C-raclopride is stereoselective. Distribution ratios [radioactivity in a brain region/"free" (not protein-bound) radioactivity in plasma] were calculated for the two enantiomers to study regional differences in the accumulation of radioactivity. The distribution ratios in white matter were similar for the two enantiomers. In the putamen, a three to four-fold higher distribution ratio was found for 11C-raclopride than for 11C-FLB472, reflecting the presence of specific binding of 11C-raclopride binding to D2-dopamine receptors in the basal ganglia. In the temporal and frontal cortices the distribution ratios were, however, only a few per cent higher for 11C-raclopride than for 11C-FLB472, indicating that if D2-dopamine receptors are present in the human neocortex, then their density is indeed very low.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Adult
  • Animals
  • Binding, Competitive
  • Brain / diagnostic imaging
  • Brain / metabolism*
  • Humans
  • Male
  • Raclopride
  • Rats
  • Receptors, Dopamine / metabolism*
  • Salicylamides / metabolism*
  • Stereoisomerism
  • Tomography, Emission-Computed


  • Receptors, Dopamine
  • Salicylamides
  • Raclopride