Evaluation of positron-emitting SCH 23390 analogs as tracers for CNS dopamine D1 receptors.

Two positron-emitting analogs of SCH 23390, one labelled with 75Br (or 76Br) and another with 11C, were evaluated as potential PET tracers for central dopamine D1 receptors. In vivo studies were performed to assess the time course of the biodistribution of these tracers in mice and to determine whether dopamine receptors mediated their uptake in the brains of these animals. Results show that indeed cerebral uptake was consistent with dopamine receptor innervation, i.e. uptake and clearance was regionally consistent with the target receptors and that specific uptake was saturable. Because of the relatively rapid pharmacokinetics of this drug, 11C-labelled SCH 23390 would be best suited for PET imaging although the metabolism of this compound needs to be further examined.