Suppression of Pentylenetetrazole Seizures by Oral Administration of a Dihydropyridine Ca2+ Antagonist

Summary: We previously demonstrated that the dihydropyridine calcium channel blocker, nimodipine, is an effective anticonvulsant in experimental seizures when administered parentally. Reported now are the results for the oral administration of nimodipine in pentylenetetrazole (PTZ)‐induced seizures in the rabbit. Twenty rabbits were randomly assigned into 10 controls and 10 treated with nimodipine 5 mg/kg/day orally for 5 days. All animals received increasing doses of the convulsant PTZ intravenously (i.v). The epileptogenecity of this agent was assessed in all animals (mg/kg) by four electrocorti‐cographic criteria: first seizure >5 s, two seizures within 5 min, epileptiform activity for 1 h, and status epilepticus. In all four categories, nimodipine increased the seizure threshold by 50–60%. The dose of PTZ required to produce the first seizure was 27.0 ± 5.4 mg/kg in controls and 49.6 ± 9.9 mg/kg in treated animals (p < 0.001). Similar values were obtained for the other three electrocorti‐cographic categories. There were no observable adverse side effects. The results confirm our previous findings that calcium influx is critical for seizure induction, and that selective central nervous system (CNS) calcium channel blockers may emerge as a new class of anticonvulsants.