Background Febrile seizures associated with fevers typically greater than 38°C are the most common convulsive event in infancy and childhood. The worldwide incidence of febrile seizures is approxi¬mately 2%–5% of the population. Increasing evidence shows close relation between inflammatory and immune processes and the pathogenesis of seizures. Based on the related studies, some of the inflammatory mediators such as cytokines, prostaglandins and complement factors, play a more prominent role in promoting inflammation and seizure. It looks probable that interfering with these molecules or their receptors can affect seizure. We aimed to determine the relationship between Toll-like receptor 4 antagonizing in febrile seizure with seizure severity and also the expression of this receptor on hippocampus of rat pups. Materials & Methods: Febrile seizure was induced by hyperthermia during p9-p11 in wistar male rats by a heated chamber. The animals were divided into 7 groups -n=8 for each-: Control, that is completely intact, Sham, hyperthermia that received Dimethyl sulfoxide as a solvent. 3rd group was hyperthermia without any injections. In other 3 experimental groups -treatments- different doses of TLR4 receptor antagonist -TAK-242- was injected. 7th group was positive control -pups received the effective dose of antagonist without hyperthermia-. For febrile seizure induction rat pups were placed into chamber preheated to 48±1°C individually, with continuous behavioral video monitoring for experiment-blind offline analysis convulsive behaviors. Then the rats’ hippocampi were dissected out on ice 6 hours after hyperthermia, frozen and used for measuring TLR4 expression. Results:The results showed that dose-dependent TAK-242 injection significantly affected the seizure parameters such as the onset and the number of seizure behavioral signs of febrile convulsions in treatment groups -P <0.05 and P <0.01, respectively-. Western blot analysis showed an increase in protein levels of neuroinflammatory receptor in sham and patient groups -P <0.05- while the protein level in treatment with TLR4 antagonist decreased in the hippocampus -P <0.05 -. Conclusion: It is suggested that this antagonist for TLR4 can reduce the seizure severity, protein expression in hippocampus and increase the onset time of seizure caused by febrile seizure and provide a reliable route to prevent febrile seizure consequences.

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