NOS1 and major depressive disorder: Hence, to explore the role of the nNOS signaling in the pathophysiology of depression and the mechanism underlying antidepressant action, we investigated the expression changes of nNOS, nNOS adaptor protein carboxy-terminal PDZ ligand of nNOS (CAPON), and the downstream physiological target protein Dexras1 in chronic unpredictable mild stress (CUMS) rats.