CHRNA7 and depressive disorder: Additionally, after exercise, the ratio of tryptophan to large neutral amino acids (TRP/LNAA) and the ratio of tryptophan to branched-chain amino acids (BCAA) increase, along with the upregulation of M5 receptors and nicotinic acetylcholine receptor α7 (nAChRα7) expression, significantly enhancing dopamine and acetylcholine levels, which in turn improves depression [132].