We studied the molecular events set into motion by stimulation of D1-like receptors downstream of Na+-K+-ATPase, while measuring apical-to-basal ouabain-sensitive, amphotericin B-induced increases in short-circuit current in opossum kidney (OK) cells. The D1-like receptor agonist SKF-38393 decreased Na+-K+-ATPase activity (IC50, 130 nM). This effect was prevented by the D1-like receptor antagonist SKF-83566, overnight cholera toxin treatment, the protein kinase A (PKA) antagonist H-89, or the PKC antagonist chelerythrine, but not the mitogen-activated PK inhibitor PD-098059 or phosphatidylinositol 3-kinase inhibitors wortmannin and LY-294002. Dibutyryl cAMP (DBcAMP) and phorbol 12,13-dibutyrate (PDBu) both effectively reduced Na+-K+-ATPase activity. PKA downregulation abolished the inhibitory effects of SKF-38393 and DBcAMP but not those of PDBu. PKC downregulation abolished inhibition by PDBu, SKF-38393, and DBcAMP. The phospholipase C (PLC) inhibitor U-73122 prevented inhibition by SKF-38393 and DBcAMP. However, DBcAMP increased PLC activity. Although OK cells express both Gsα and Gq/11α proteins, D1-like receptors are coupled to Gsα proteins only, as evidenced by studies in cells treated overnight with specific antibodies raised against Gsα and Gq/11α proteins. We conclude that PLC and Na+-K+-ATPase are effector proteins for PKA and PKC, respectively, after stimulation of D1-like receptors coupled to Gsα proteins, in a sequence of events that begins with adenylyl cyclase-PKA system activation followed by PLC-PKC system activation.