NOS1 and Anxiety: Previously, we demonstrated that high concentration of glucocorticoids after stress upregulated nNOS via mineralocorticoid receptor (MR) in the DG of the hippocampus.17 Altogether, these evidences support a novel hypothesis of anxiety that chronic stress‐induced nNOS overexpression reduce the expression of 5‐HT1A receptor in the DG, causing a higher level of nNOS, which in turn lead to more severe deficiency of 5‐HT1A receptor in the DG.