High affinity binding for pramipexole, a dopamine D3 receptor ligand, in rat striatum

Quantitative autoradiography of rat brain slices was carried out with eight concentrations of [3H]pramipexole, a dopamine D3 receptor-preferring ligand. Saturation analysis revealed high affinity pramipexole binding (Kd = 0.2-0.4 nM) in the islets of Calleja, nucleus accumbens, olfactory tubercle, and anterior caudate. Since these affinities resemble pramipexole's affinity for the high affinity state of the rat dopamine D3, but not D2 receptors, it is possible that dopamine D3 receptors have greater presence in caudate than has heretofore been appreciated.