X. Guo et al., CHARACTERISTICS OF TETRAHYDROPROTOBERBERINES ON DOPAMINE D-1 AND D-2 RECEPTORS IN CALF STRIATUM, Zhongguo yaoli xuebao, 18(3), 1997, pp. 225-230
AIM: To study the characteristics of tetrahydroprotoberberines (THPB)
on dopamine D-1 and D-2 receptors and elucidate their structure-activi
ty relationship. METHODS: Radioligand assay in vitro with a two-site m
odel program analysis. RESULTS: Four THPB with two hydroxyl groups on
C-2 and C-9 or C-2 and C-10 exhibited R-H and R-L two binding sites to
D-1 receptors and guanosine triphosphate regulated the R-H binding si
te of SPD and THPB-132A in competition assay, while eleven THPB includ
ing nonhydroxy-THPB, monohydroxy-THPB, and THPB with two hydroxyl grou
ps attaching to C-3 and C-10 showed one binding site to D-1 receptors
under the same conditions. However, the tested eleven THPB all manifes
ted one binding site to D-2 receptors in competition assay, and the 2-
hydroxy-THPB had the most potent affinity for D-2 receptors. CONCLUSIO
N: Dihydroxy-THPB with two hydroxyl groups attaching to C-2 and C-9 or
C-2 and C-10 possess the intrinsic activity of agonist to D-1 recepto
rs, while the other THPB do not. The tested eleven THPB all are the an
tagonists of D-2 receptors.