Effect of antiepileptic drugs and calcium channel blocker on hyperthermic seizures in rats: animal model for hot water epilepsy.

Hyperthermic seizures were elicited in groups of freely ambulant rats with jets of hot water of 55 degrees C on the head for about 10 mins. Bipolar depth EEG from the hippocampus and the behavioural seizures following the stimulation were recorded. The rectal temperature (threshold) for seizure initiation was 41.5 degrees C. The seizures were predominantly clonic jerks accompanied by large spikes and slow waves lasting for 30-60s. After 3 stimulations (once a day), Phenobarbitone (Pb) 0.02 mg/g daily, Diphenylhydantoin (DPH) 0.001 mg/g, 0.005 mg/g and 0.04 mg/g. daily and Nifedipine (Nif) 0.005 mg/g twice daily were administered intraperitoneally in different rats. During the 10-days injection trials, Pb completely suppressed seizures whereas DPH and Nif did not have any effect. One of the rats with DPH showed increased epileptic activity. After a 10 day 'washout' period' Pb and DPH were interchanged and again the rats were tested for seizures on 10 days. On changing over to Pb from DPH there was complete suppression of seizures and electrical seizure discharges. Whereas those rats which earlier had no seizure activity with Pb started showing the same on changing over to DPH.