Background: Seizure is an abnormal electrical activity probably due to an imbalance between excitation and inhibition in the brain. Pentylenetetrazol (PTZ) is a chemical convulsive agent abundantly used in laboratory animals. PTZ induces a change in glutamate and GABA in the brain which this study investigates the persistence of this change.

Materials and Methods: In this experimental study, 18 male Wistar rats divided into 3 groups. Three i.v doses of PTZ 20, 25 and 30 mg/ml were used to determine the effective PTZ dose. Convulsive behaviors were monitored as tonic clonic and myoclonic twitches. Hippocampal glutamate and GABA contents were measured using a biochemical method.

Results: Dose of 20 was resulted in long latency to and short lasting TC convulsions with a high volume of injected PTZ solution. On the other hand, dose of 25 and 30 led to short latency and long lasting convulsions with low volume of injecting solution. However there was high rate of mortality (100%) in dose of 30 mg/ml. Hippocampal glutamate content was decreased in zero and 20 min groups while GABA content was decreased only in 20 min group.

Conclusion: It is concluded that dose of 25 is the appropriate i.v dose to induce TC convulsions in rats which decreases glutamate and GABA while increases the ratio of glutamate to GABA. Therefore, alteration of glutamate and GABA may be the basis for subsequent seizure induced changes.