OBJECTIVE To explore the safe and effective dose of sirolimus (Rapamycin,Sir) and its effect on seizure comorbidities. METHODS Immature C57BL/6 mice at postnatal 10 d of age were administered with kainic acid(KA) 12.0 mg · kg-1 intraperitoneally by a single injection to induce acute seizure. Sir 0.3, 1.0 and 3.0 mg · kg-1 was injected 24 h after seizure every other day until 3 d, 1 week, 3 weeks, 5 weeks and 6 weeks. Western blotting analysis was used to detect the expression and phos?phorylation level of S6 protein and to determine the minimum effective dose of Sir. Effect of the mini?mum effective dose of Sir on cognitive function and body growth was observed by several evaluations. Immunofluorescent intensity of Doublecortin (DCX) immunofluorescent staining was conducted to evaluate the development of neurons in the hippocampus. Morris water maze was used to assess the cognitive function. Tail suspension test, O maze and new object recognition test were used to study the anxiety-like behaviors of mice. RESULTS The result of Western blotting showed that Sir 0.3 mg · kg-1 had no significant effect on the phosphorylation of S6 protein in normal mice or KA mice, whereas 1.0 and 3.0 mg · kg- 1 could significantly inhibit the phosphorylation of S6 protein in KA mice (P<0.05). Sir 1.0 mg·kg-1 had no obvious effect on DCX-positive cells or body wass. Morris water maze showed that KA-induced seizure resulted in prolonged escape latency and swimming length (P<0.05), and a decreased crossing number of target quadrant (P<0.05). Sir 1.0 mg·kg-1 significantly reversed the deficit of cognitive function of KA-induced seizure mice (P<0.05), whereas no significant difference was found between Sir group and normal control group. Compared with normal control group, model group showed increased freezing time in tail suspension test (P<0.05), decreased migration length and reten?tion time in open arms in O maze (P<0.05), decreased retention time and touch frequency with new objects, migration length and average speed in new object recognition test (P<0.05). Sir 1.0 mg · kg-1 significantly reversed the above anxiety and depression status, whereas no significant difference was found between sirolimus group and normal control group. CONCLUSION Sir 1.0 mg · kg-1 inhibits the abnormal activation of mTOR pathway and the formation of epilepsy comorbidity in immature mice. Along with its mild side effect in development, Sir 1.0 mg · kg-1 will be an ideal dose to be used in the treatment of seizure in immature mice.