Effects of carbamazepine, clonazepam, and phenytoin on seizure threshold in amygdala and cortex.

This experiment was designed to determine whether or not the stronger effect of anticonvulsants on cortex than on amygdala focal seizures was due to a greater elevation of cortex seizure threshold. The effects of several doses of carbamazepine, clonazepam, and phenytoin were examined on the threshold for electrically induced afterdischarge in amygdala and cortex in 71 rats. All three drugs were found to be effective in increasing the seizure threshold with greater effects being produced in the cortex than in the amygdala. Carbamazepine produced the largest threshold increase in both foci, and clonazepam produced the weakest effects. These data are comparable to previous data on drug action against focal or partial seizures, and suggest that anticonvulsants may control partial attacks through their action on the local seizure threshold. This theory of anticonvulsant drug action adds to the common belief that carbamazepine and phenytoin act primarily by blocking seizure spread.