AVPR2 and autosomal dominant polycystic kidney disease: The identification of cAMP and PKA signaling as a therapeutic target [6–9] has led to clinical trials of vasopressin V2 receptor (V2R) antagonists and somatostatin analogs [10, 11] and to the recent approval of the V2R antagonist, tolvaptan, for the treatment of ADPKD with rapidly progressive renal disease in Japan, Canada, the European Union, Switzerland and South Korea.