DEVELOPMENT OF CENTRAL 5-HT2A RECEPTOR RADIOLIGANDS FOR PET - COMPARISON OF [H-3] RP-62203 AND [H-3] SR-46349B KINETICS IN RAT-BRAIN

[H-3]RP 62203 and [H-3]SR 46349B binding were assessed in rat brain af ter intravenous (iv) injection. The distribution of specific binding o f each radioligand corresponded to the known distribution of 5-HT2A re ceptor sites. The maximum signals (counts/g tissue over counts/g cereb ellum) given by [H-3]RP 62203 and [H-3]SR 46349B were 9.0 +/- 0.9 at 6 0 min and 3.2 +/- 0.3 at 30 min, respectively, in frontopolar cortex. Specific binding was quantified using a reference-tissue compartment m odel, RP 62203 appears to be more suitable than SR 46349B for developm ent as a PET radioligand on the basis of its higher receptor specific signal.