CHRNA7 and depressive disorder: In addition, KYNA is also a noncompetitive antagonist of low concentrations of alpha-7 nicotinic acetylcholine receptor (α7 nAChR), which is associated with learning and memory (Banerjee et al., 2012), and reduced KYNA levels may be involved in the pathophysiological mechanisms of depression by inhibiting α7 nAChR.