COMPARISON OF THE EFFECTS OF PROPOFOL AND THIOPENTAL ON THE PATTERN OF MAXIMAL ELECTROSHOCK SEIZURES IN THE RAT

The anticonvulsant effects of propofol and thiopental (thiopentone) we re determined by measuring the durations of the various phases of maxi mal electroshock seizures in the rat. Five min. after intraperitoneal administration of subanaesthetic (6.25, 12.5 and 25 mg/kg) and 50 mg/k g doses of propofol, the 2 highest doses abolished both tonic hindlimb extensor phases (full and partial extension) in all rats and decrease d the duration of the total tonic phases of the seizure. Although the lowest dose produced no effect, the 12.5 mg/kg dose decreased the dura tion of both the full and partial tonic extensor phases and increased the duration of tonic flexion, showing that even this low dose had ant iconvulsant activity. Subanesthetic doses of thiopental (5, 10 and 20 mg/kg) produced similar changes in the maximal electroshock seizures e xcept that even the lowest dose also significantly decreased the durat ion of total extension and total tonus. Postseizure depression was pro longed only by the highest dose of propofol Thus, even low doses of ei ther propofol or thiopental, that produced only minimal behavioural ef fects, had marked anticonvulsant effects against electrically induced convulsions in the rat. No evidence of enhanced convulsant maximal ele ctroshock seizures patterns was observed at any dose.