Antiseizure medication is the mainstay of treatment for seizures, and adjunctive therapy is widely used to achieve adequate seizure control in patients with epilepsy who fail to respond to the first monotherapy. The newly developed antiepileptic drug cenobamate (YKP3089) as an adjunctive therapy improved seizure control in patients with uncontrolled focal seizures. Cenobamate is thought to reduce neuronal excitability through action on multiple targets, including GABA A receptors (GABAARs) and voltage-gated sodium channels. However, its effects on brain function and synaptic plasticity are unclear. Here, we explored the behavioral, synaptic, and cellular actions of cenobamate. Cenobamate influenced novel object recognition, object location memory, and Morris water maze performance in mice. Cenobamate enhanced inhibitory postsynaptic potentials by prolonging inhibitory postsynaptic current (IPSC) decay without affecting presynaptic GABA release or the peak amplitude of IPSCs. In addition, cenobamate suppressed hippocampal excitatory synaptic transmission by reducing the excitability of Schaffer collaterals and interfered with the induction of long-term potentiation. A reduction in neuronal excitability induced by cenobamate was associated with an elevation of action potential (AP) threshold, and which progressively increased in later APs during repetitive firing, indicating the activity-dependent modulation of neuronal sodium currents. Cenobamate suppressed neuronal excitability under the condition that GABAergic neurotransmission is excitatory, and administration of cenobamate rapidly enhanced the phosphorylation of eukaryotic elongation factor 2 in the hippocampus of adult and neonatal mice. Collectively, these results suggest that the combined action of cenobamate on sodium currents and GABAAR-mediated synapse responses results in reduced excitability in neurons.
Keywords: Behavior; Cenobamate; Epilepsy; Memory; Plasticity; Synapse.
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