Studies on Substituted Benzamides as Brain Dopamine Receptor Imaging Agent

Abstract

Several new amino group and acetylamino group substituted benzamides and their ¹²⁵I labeled compounds were synthesized. The IC₅₀ of (RS)—2—methoxy—4—amino—5—bromo—N—[(1—ethyl—2—pyrrolidinyl) methyl] benzamide was 0.0164 µmol/L, IC₅₀ of sulpride and haloperidol being 0.0991 µmol/L and 0.0156 µmol/L respectively. It showed high affinity for dopamine D₂ receptor in vitro. The ratio of striatum to cerebellum and the ratio of striatum to cortex of [¹²⁵I]—(RS)—2—methoxy—4—acetylamino—5—iodo—N—[(1—ethyl—2—pyrrolidin yl) methyl] benzamide in rats at 60 min after injection were 6.75 respectively. When labeled with ¹²³I, it may be uesful for imaging brain dopamine D₂ receptor.