OBJECTIVETo investigate the effect of Shuyusan decoction on neuropeptide Y (NPY) and serotonin (5-HT) expression in the hippocampus and plasma of rats with chronic mild unpredictable stressors depression.

METHODSFifty Wistar rats were randomly divided into 5 groups, namely the normal control group, model group, fluoxetine group, and high- and low-dose Shuyusan groups. Except for those in the normal control group, all the rats were subjected to chronic mild unpredicted stress for 21 consecutive days with corresponding treatments. Open-field test was used to assess the behavioral changes of the rats. The content of NPY in the hippocampus and plasma was detected by competitive enzyme-linked immunosorbent assay, and immunocytochemistry was used to determine the expression of 5-HT in the hippocampus.

RESULTSNPY levels in the hippocampus and plasma was significantly decreased in the model group as compared with that in the normal control group (P<0.05). Treatments with fluoxetine and high-dose Shuyusan both significantly increased NPY levels in the hippocampus and plasma in the depressive rats (P<0.05), resulting also in significantly increased 5-HT-immunoreactive neurons in the cerebral cortex and hippocampus and the average optical density (P<0.05).

CONCLUSIONShuyusan decoction can effectively increase plasma and hippocampus NPY levels and the number of 5-HT-positive neurons in the cerebral cortex and happocampus of rats with chronic mild unpredictable stress-induced depression.