High Affinity and Selectivity of Some Tetrahydroprotoberberine Alkaloids for Rat Striatal3H-raclopride Binding Sites

Four tetrahydroprotoberberine alkaloids isolated from Guatteria ouregou and Guatteria schomburgkiana were tested for their ability to displace 3H-SCH23390 and 3H-raclopride from their specific dopaminergic striatal binding sites and to inhibit 3H-dopamine uptake by striatal synaptosomes. All of them displaced 3H-raclopride binding with a high affinity and a great selectivity. These data suggest that the tetrahydroprotoberberine skeleton could be very interesting for developing selective ligands of D2 dopamine receptors.