Effects of gypenosides on chronic stress-induced anxiety in mice

Abstract

The objective of present study was to investigate the effects of gypenosides (GPS), the gypenosides-enriched components of Gynostemma pentaphyllum, on chronic stress-induced anxiety in mice. Animals were treated with GPS (50, 100 and 200 mg/kg, oral) for 10 days before the exposure to chronic electric footshock (EF) stress (intensity 2 mA, interval 10 s and duration 3 min). The chronic stressed-group showed anxiety disorders in elevated plus maze compared with control group. However, the treatment of GPS ameliorated the anxiety disorders induced by chronic EF stress. The spontaneous locomotor activities were decreased by ca. 18.1% (P < 0.05) by chronic EF stress compared with control group (n = 10). The spontaneous locomotor activities decreased were increased by ca. 9.4%, 15.3% (P < 0.05) and 15.9% (P < 0.05) by treatment with GPS (50, 100 and 200 mg/kg). Furthermore, the levels of dopamine and serotonin in the brain were decreased by ca. 26.6% (P < 0.05) and 25.1% (P < 0.05) after being exposed to chronic EF stress compared with control group (n = 10). The levels of dopamine and serotonin were inceased by ca. 11.4%, 18.0% (P < 0.05), 16.6% (P < 0.05) and 9.1%, 17.6% (P < 0.05), 15.7% (P < 0.05), respectively, by GPS (50, 100 and 200 mg/kg) compared with chronic EF stressed-group (n = 10). Finally, chronic EF stress-induced c-Fos expression in the brain was markedly increase by ca. 188% (P < 0.01) compared with control group. However, the number of c-Fos-immunoreactive cells were significantly decreased by ca. 19.4% (P < 0.05), 30.2% (P < 0.01) and 24.3% (P < 0.05) by treatment with GPS (50, 100 and 200 mg/kg), compared with chronic EF stressed-group. In addition, the anxiolytic functions of GPS were compared with GP-EX, ethanol extracts from Gynostemma pentaphyllum. These results suggest that GPS have anxiolytic effects on chronic EF stress-induced anxiety disorders and GPS may serve as an herbal drug in chronic stress-induced anxiety disorders.