Quantitative evaluation of the actions of anticonvulsants against different chemical convulsants

Anticonvulsants were tested on mice for their effectiveness against different chemical convulsants. Ethosuximide is very effective against pentylenetetrazol (PTZ), but ineffective against 3-mercaptopropionate (3-MP) which is an inhibitor of gamma-aminobutyrate (GABA) synthesis. Trimethadione, chlordiazepoxide and mesuximide are less effective against 3-MP than against PTZ. The same tendency was apparent, though falling short of statistical significance, with phenobarbital, mephenytoin, carbamazepine and valproic acid, whereas aminooxyacetic acid (AOAA) appeared to be somewhat more effective against 3-MP than against PTZ. Several anticonvulsants were tested also against bicuculline (BIC), picrotoxin (PIC) and bemegride (BEM), and profiles depicting their relative capacities to antagonize the convulsants were constructed. These show major differences and few resemblances. Likewise the convulsants show little resemblance to each other in their patterns of sensitivity to different anticonvulsants. The data do not support the concept that PTZ, BEM, BIC or PIC induce seizures primarily by blockading GABA-mediated inhibition, since their patterns are so unlike that of 3-MP. The profiles of clinically used anticonvulsants suggest that none of those tested acts primarily on the GABA system, since all are so unlike that of AOAA.