Introduction: Anesthetics have some serious side effects. Previous studies showed controversial (neurodegenerative or neuroprotective) effects of barbiturates. NMDA receptors blockers or GABA receptors agonists during the critical period of development can involve in the brain development and synaptogenesis. This critical period in different species will be different and in rats it begins from 2 days before parturition and can lasts until 14 days after birth. The purpose of this study was to investigate the relation between postnatal repeated induced Thiopental anesthesia and Pentylentetrazole (PTZ) induced convulsions after maturity. Materials and methods: Wistar male neonates rats (n=20) were divided into experimental and control groups. The experimental group was deeply anesthetized with Thiopental (daily) since 10 to 20 days of postnatal period, after maturation PTZ was injected (45 mg/kg/ip) to assay the sensitivity of mature rats to PTZ induced seizures and latent period for seizures expression after injections was determined in both groups. Result and discussion: Results did not show significant difference in latent’s periods between experimental and control animals. Drugs which affect the excitatory or inhibitory receptors can show neurodegenerative effects in the critical periods of brain development but regard to Thiopental; these effects may be regenerated during growth and maturity. Also it is possible that such effects are remained for the other behaviors, it remained to investigate with more detail. Key words: Repeated Anesthesia, Thiopental, Seizure, PTZ

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