PPP1R13B and major depressive disorder: Whereas previous studies observed decreased activation of adenylate cyclase and PKA in depression (Gould and Manji, 2002; Akin et al., 2005), in this study, we found a significant decrease of PPP1R13B and PPP2R2B, two phosphate family proteins that counterbalance the action of PKA (Fimia and Sassone-Corsi, 2001), in the hippocampus.