and Objective: Hydroalcoholic extract of Melissa Officinalis (MO) has been considered as an anticonvulsant in traditional medicine. This study was done to determine its effect in prevention of convulsions induced by nicotine in mice. Methods: Normal saline (10 ml/kg) was injected to control group (i.p). After preparation of hydroalcoholic extract of MO by maceration method, doses of 200, 400, 600, 800 and 1000 mg/kg of this extract administered separately at 0, 15, 30 and 45 minutes before

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... tion of nicotine. Then intensity, duration and latency of convulsions and mortality rate were surveyed. Findings: Administration of the extract with doses of 800 and 1000 mg/kg at 15, 30 and 45 minutes and with dose of 600 mg/kg at 30 min before injection of nicotine significantly increased the latency of convulsions (P<0.05). None of administered doses changed the intensity of convulsions significantly. Conclusion: Obtained results showed that hydroalcoholic extract of Melissa Officinalis (MO) cause to increase latency and intensity of convulsions induced by Nicotine.