Serum IDO activity was negatively correlated (r = − 0.4788, P = 0.0056) with the anxiety index from the open field test, whereas serum QUIN (r = 0.3984, P = 0.0239) and serum QUIN/KYNA (r = 0.4218, P = 0.0162) were positively correlated and serum KYNA was negatively correlated (r = − 0.4398, P = 0.0118) with spatial learning during the retention phase of the Barnes maze test (Table 3). The gene discussed is IDO1; the disease is Anxiety.