In this pathway, dopamine - and an adenosine 3 ′, 5 ′ - monophosphate (cAMP)--
regulated phospho - protein of 32 kilodaltons (DARPP - 32) is phosphorylated or dephosphorylated at three sites, in a pattern predicted to cause a synergistic inhibition of protein phosphatase — 1 and concomitant regulation of its downstream effector proteins glycogen synthesis kinase — 3 (GSK - 3), cAMP response element — binding protein (CREB), and c - Fos.