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) were determined by measuring the durations of the various phases of maximal electroshock seizures in the rat. Five min. after intraperitoneal administration of subanaesthetic (6.25, 12.5 and 25 mg/kg) and 50 mg/kg doses of propofol, the 2 highest doses abolished both tonic hindlimb extensor phases (full and partial extension) in all rats and decreased 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 duration of both the full and partial tonic extensor phases and increased the duration of tonic flexion, showing that even this low dose had anticonvulsant activity. Subanesthetic doses of thiopental (5, 10 and 20 mg/kg) produced similar changes in the maximal electroshock seizures except that even the lowest dose also significantly decreased the duration of total extension and total tonus. Postseizure depression was prolonged only by the highest dose of propofol Thus, even low doses of either propofol or thiopental, that produced only minimal behavioural effects, had marked anticonvulsant effects against electrically induced convulsions in the rat. No evidence of enhanced convulsant maximal electroshock seizures patterns was observed at any dose.