Presynaptic Effect of Ethosuximide: a Study on a Cell-Free Model System

The effect of an antiepileptic drug, ethosuximide, on fusion of synaptic vesicles with the synaptosomal plasma membranes was studied. It was shown that ethosuximide increases the rate of the Ca²⁺-dependent fusion reaction. We found that ethosuximide-induced fusion of synaptic vesicles with the plasma membrane in a Ca²⁺-free medium is much lower than the Ca²⁺-induced effect under the same conditions. Thus, the fusion-inducing effect of ethosuximide is mostly Ca²⁺-dependent. Ethosuximide-evoked fusion was suppressed by pentylenetetrazole.