Effect of dexamethasone on the convulsive behavior induced by hyperthermia: possible role of histamine

Febrile seizures are the most common seizure disorder in childhood and its prevalence is estimated to be 2 to 5 percent. There is a relationship between the use of corticosteroids and seizures. This study investigated the effects of dexamethasone pretreatment on convulsive behavior caused by hyperthermia. In this study, 24 rats aged 19-20 days were divided into 3 groups (n=8) as control, hyperthermia and dexamethasone. In the hyperthermia group, rats were placed in the chamber for 30 min and warm wind was blown on them. In the dexamethasone group, the rats received intraperitoneal dexamethasone before hyperthermia. The body temperature of the rats was continuously recorded via a rectal probe throughout the experiment. During 30 min of hyperthermia, behavior of each rat was carefully observed and recorded. Blood sampling was done from the heart and samples were used to measure histamine blood levels. All the rats that were exposed to hyperthermia showed convulsive behavior. Dexamethasone potentiated seizure intensity and significantly increased the rate of tonic-clonic seizure (5.62±1.05 in dexamethasone and 1.37±0.46 in hyperthermia) (p=0.02). Hyperthermia decreased histamine blood levels and dexamethasone potentiated this reduction (p<0.001). At least one of the ways that hyperthermia leads to seizure is through the reduction of histamine blood level. Since histamine has an anticonvulsant effect, reduction of histamine blood level is one reason of hyperthermia -induced seizure. Dexamethasone leads to a deacrease in histamine blood level and potentiates hyperthermia-induced seizure.