Topiramate depresses carbachol-induced plateau potentials in subicular bursting cells.

Intracellular recordings were made in an in vitro slice preparation to establish whether the antiepileptic drug topiramate reduces the depolarizing plateau potentials (PPs) induced in the rat subiculum by intracellular pulses of depolarizing current, in the presence of the cholinergic agonist carbachol (CCh, 70-100 microM). PPs lasted up to about 2 s, and disappeared during application of the muscarinic receptor antagonist atropine. Topiramate (10-100 microM, n = 22 neurons) decreased and eventually abolished in a dose-dependent manner these PPs, even when the function of excitatory amino acid and GABAA receptors was blocked. Hence, topiramate depresses muscarinic receptor-dependent PPs in the rat subiculum, thus suggesting that this form of excitation may represent a target for the mechanism of action of this antiepileptic compound.