Antidepressant-like effect of genipin in mice

The present study aimed to investigate the antidepressant potential of genipin and its possible mechanisms. Mouse models of depression including the forced swimming test (FST) and the tail suspension test (TST) were used to evaluate the effects of genipin. A possible mechanism was explored in the test of antagonism of reserpine-induced ptosis and hypothermia in mice. The contents of monoamine neurotransmitters and their metabolites including epinephrine (NE), 5-hydroxytryptamine (5-HT) and 5-hydroxyindoleacetic acid (5-HIAA) in mice hippocampi were determined by HPLC–ECD. The results showed that intra-gastric administration of genipin at 50, 100, 200 mg/kg or fluoxetine at 7.5 mg/kg for 7 days significantly reduced the duration of immobility in FST and TST, while it did not affect the locomotor activity in the open field test (OFT). However, the effect was not dose-dependent. When the mice were treated with genipin or fluoxetine for 7 days, both of them could antagonize reserpine-induced ptosis and hypothermia. The 5-HT and NE contents in mice hippocampi were decreased after the peritoneal injection of reserpine at 2.0 mg/kg. The pre-treatment with genipin at 50, 100, 200 mg/kg or fluoxetine at 7.5 mg/kg for 7 days could elevate the contents of NE and 5-HT in mice hippocampi significantly. The results suggest that compared with fluoxetine, genipin exerts antidepressant-like effects significantly. A possible mechanism, at least in part, is the regulation of the 5-HT and NE levels in the hippocampus.