Cognitive and behavioral effects of the anti-epileptic drug cenobamate (YKP3089) and underlying synaptic and cellular mechanisms.

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.

Syringaresinol suppresses excitatory synaptic transmission and picrotoxin-induced epileptic activity in the hippocampus through presynaptic mechanisms.

Many neuromodulating drugs acting on the nervous system originate from botanical sources. These plant-derived substances modulate the activity of receptors, ion channels, or transporters in neurons. Their properties make the substances useful for medicine and research. Here, we show that the plant lignan (+)-syringaresinol (SYR) suppresses excitatory synaptic transmission via presynaptic modulation. Bath application of SYR rapidly reduced the slopes of the field excitatory postsynaptic potentials (fEPSPs) at the hippocampal Schaffer collateral (SC)-CA1 synapse in a dose-dependent manner. SYR preferentially affected excitatory synapses, while inhibitory synaptic transmission remained unchanged. SYR had no effect on the conductance or the desensitization of AMPARs but increased the paired-pulse ratios of synaptic responses at short (20-200 ms) inter-stimulus intervals. These presynaptic changes were accompanied by a reduction of the readily releasable pool size. Pretreatment of hippocampal slices with the Gi/o protein inhibitor N-ethylmaleimide (NEM) abolished the effect of SYR on excitatory synaptic transmission, while the application of SYR significantly decreased Ca2+ currents and hyperpolarized the resting membrane potentials of hippocampal neurons. In addition, SYR suppressed picrotoxin-induced epileptiform activity in hippocampal slices. Overall, our study identifies SYR as a new neuromodulating agent and suggests that SYR suppresses excitatory synaptic transmission by modulating presynaptic transmitter release.

The atypical antipsychotic olanzapine disturbs depotentiation by modulating mAChRs and impairs reversal learning.

Antipsychotic medication is an essential component for treating schizophrenia, which is a serious mental disorder that affects approximately 1% of the global population. Olanzapine (Olz), one of the most frequently prescribed atypical antipsychotics, is generally considered a first-line drug for treating schizophrenia. In contrast to psychotic symptoms, the effects of Olz on cognitive symptoms of schizophrenia are still unclear. In addition, the mechanisms by which Olz affects the neural circuits associated with cognitive function are unknown. Here we show that Olz interrupts depotentiation (reversal of long-term potentiation) without disturbing de novo LTP (long-term potentiation) and LTD (long-term depression). At hippocampal SC-CA1 synapses, inhibition of NMDARs (N-methyl-d-aspartate receptors), mGluRs (metabotropic glutamate receptors), or mAChRs (muscarinic acetylcholine receptors) disrupted depotentiation. In addition, co-activation of NMDARs, mGluRs, and mAChRs reversed stably expressed LTP. Olz inhibits the activation of mAChRs, which amplifies glutamate signaling through enhanced NMDAR opening and Gq (Gq class of G protein)-mediated signal transduction. Behaviorally, Olz impairs spatial reversal learning of mice in the Morris water maze test. Our results uncover a novel mechanism underpinning the cognitive modulation of Olz and show that the anticholinergic property of Olz affects glutamate signaling and synaptic plasticity.