OBJECTIVE: To investigate the antiepileptic effects of Chaihushugan decoction(CHSGD) in rats with pentylenetetrazole(PTZ)-induced seizures and to discuss the impact of CHSGD on glutamate metabolism, a hypothesized underlying mechanism of seizure reduction.METHODS: Fifty Wistar rats were divided randomly into either control(n = 10) or experimental(n = 40)groups. Rats in the control group were administered physiological saline intraperitoneally. A subconvulsive dose of PTZ(35 mg/kg) was administered intraperitoneally to rats in the experimental group to induce seizures. The fully PTZ-kindled rats were then randomly divided into five subgroups(n = 8 each) based on the following treatment categories: physiological saline, VPA(200 mg/kg), CHSGD(2.5 g/kg), CHSGD(5 g/kg), or CHSGD(10 g/kg),administered orally once per day, respectively. On day 28 following initiation of drug treatment, seizures were monitored. The rats were then sacrificed, and hippocampal dissections were performed for subsequent studies.RESULTS: CHSGD significantly prolonged the latency of myoclonic, clonic, and tonic seizures, while decreasing overall seizure rates in the kindled rats.The measured concentrations of 2-[N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl) amino]-2-deoxy-d-glucose(2-NBDG) and glutamate were significantly lower in the hippocampi of kindled rats in groups treated with CHSGD compared with those treated with PTZ alone. In addition, CHSGD was found to up-regulate both the expression of glutamate transporter-1(GLT-1) protein and the activity of glutamine synthetase(GS) in the hippocampi of kindled rats.CONCLUSION: These results suggest that CHSGD has antiepileptic effects on PTZ-induced seizures.The results further suggest an increase in glutamate metabolism at the synaptic cleft is a putative underlying mechanism of seizure reduction.