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Mutations of the SCN1A gene, which encodes the voltage-dependent Na + channel's α subunit, are associated with diverse epileptic syndromes ranging in severity, even intra-family, from febrile seizures to epileptic encephalopathy. The underlying cause of this variability is unknown, suggesting the involvement of additional factors. The aim of our study was to describe the properties of mutated channels and investigate genetic causes for clinical syndromes' variability in the family of five SCN1A gene p.Arg1596Cys mutation carriers. The analysis of additional genetic factors influencing SCN1A -associated phenotypes was conducted through exome sequencing (WES). To assess the impact of mutations, we used patch clamp analysis of mutated channels expressed in HEK cells and in vivo neural excitability studies (NESs). In cells expressing the mutant channel, sodium currents were reduced. NESs indicated increased excitability of peripheral motor neurons in mutation carriers. WES showed the absence of non-SCA1 pathogenic variants that could be causative of disease in the family. Variants of uncertain significance in three genes, as potential modifiers of the most severe phenotype, were identified. The p.Arg1596Cys substitution inhibits channel function, affecting steady-state inactivation kinetics. Its clinical manifestations involve not only epileptic symptoms but also increased excitability of peripheral motor fibers. The role of Nav1.1 in excitatory neurons cannot be ruled out as a significant factor of the clinical phenotype.

Recent findings suggest an important role for the dysregulation of stromal interaction molecule (STIM) proteins, activators of store-operated Ca 2+ channels, and the prolonged activation of N-methyl-D-aspartate receptors (NMDARs) in the development of neurodegenerative diseases. We previously demonstrated that STIM silencing increases Ca 2+ influx through NMDAR and STIM-NMDAR2 complexes are present in neurons. However, the interplay between NMDAR subunits (GluN1, GluN2A, and GluN2B) and STIM1/STIM2 with regard to intracellular trafficking remains unknown. Here, we found that the activation of NMDAR endocytosis led to an increase in STIM2-GluN2A and STIM2-GluN2B interactions in primary cortical neurons. STIM1 appeared to migrate from synaptic to extrasynaptic sites. STIM2 silencing inhibited post-activation NMDAR translocation from the plasma membrane and synaptic spines and increased NMDAR currents. Our findings reveal a novel molecular mechanism by which STIM2 regulates NMDAR synaptic trafficking by promoting NMDAR endocytosis after receptor overactivation, which may suggest protection against excessive uncontrolled Ca 2+ influx through NMDARs., (© 2023. The Author(s).)

TREK-2-like channels in the pyramidal neurons of rat prefrontal cortex are characterized by a wide range of spontaneous activity-from very low to very high-independent of the membrane potential and the stimuli that are known to activate TREK-2 channels, such as temperature or membrane stretching. The aim of this study was to discover what factors are involved in high levels of TREK-2-like channel activity in these cells. Our research focused on the PI(4,5)P2-dependent mechanism of channel activity. Single-channel patch clamp recordings were performed on freshly dissociated pyramidal neurons of rat prefrontal cortexes in both the cell-attached and inside-out configurations. To evaluate the role of endogenous stimulants, the activity of the channels was recorded in the presence of a PI(4,5)P2 analogue (PI(4,5)P2DiC8) and Ca 2+ . Our research revealed that calcium ions are an important factor affecting TREK-2-like channel activity and kinetics. The observation that calcium participates in the activation of TREK-2-like channels is a new finding. We showed that PI(4,5)P2-dependent TREK-2 activity occurs when the conditions for PI(4,5)P2/Ca 2+ nanocluster formation are met. We present a possible model explaining the mechanism of calcium action.

Valproic acid has a long-standing reputation of effectively treating the symptoms of not only epilepsy but also psychiatric conditions. In the latter, the exact mechanism by which valproate exerts its effect remains unclear. In this study, epileptiform bursts were recorded from pyramidal neurons in the prefrontal cortex (the brain region thought to be involved in psychiatric disorders) using the patch-clamp technique. An extracellular solution with no magnesium ions and elevated potassium levels that is known to induce epileptiform activity in vitro was used. Because of their short durations, the epileptiform bursts were regarded as interictal-like epileptiform activity, which is believed to be involved in cognitive impairment. Interictal discharges occur in many neuropsychiatric disorders as well as in healthy population. Epileptic activity in prefrontal cortex pyramidal neurons was potently inhibited by two therapeutic concentrations of valproic acid (20 μM and 200 μM). Moreover, valproate suppressed spontaneous excitatory postsynaptic potentials. Epileptiform bursts were fully inhibited by NMDA receptor antagonist, which suggests that epileptiform activity is driven by NMDA receptors. The inhibition of excitability in prefrontal cortex pyramidal neurons by valproate was also shown. This study shows that it is possible to evoke NMDA-dependent epileptiform activity in prefrontal cortex pyramidal neurons in vitro. We suggest that the prefrontal cortex is a good region for studying the influence of drugs on interictal epileptiform activity., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Short-term treatment with large doses of corticosteroids can result in acute weakness of muscles in processes that have not yet been fully characterized. Corticosteroids have been shown to exert direct inhibitory action on the muscle-type nicotinic acetylcholine receptor (AChR), and therefore can promote pharmacological muscle denervation. The mechanism of hydrocortisone (HC) blockage of AChR has not been fully established yet. It is uncommon for an electrically neutral molecule, for example, HC, to induce voltage-dependent changes in AChR kinetics. Our experiments aimed to determine the source of voltage-dependency in HC action. Wild-type (WT) and αD200Q receptors were transiently expressed in HEK293 cells. Recordings were performed in either the presence or absence of HC. We showed that the D-to-Q substitution is capable of suppressing the voltage dependency in the HC-induced block. We conclude that the distance between αD200 and the agonist-binding site depends on the membrane potential. The voltage-dependent changes of the αD200 position have not been considered yet. To our knowledge, the ability to induce voltage-dependency in blocker action has not been shown previously for an amino acid located outside the transmembrane portion of the receptor. Possible mechanisms of HC block (allosteric and knocking) in WT and αD200Q receptors are discussed., (© 2018 John Wiley & Sons A/S.)

Developmental changes that occur in the prefrontal cortex during adolescence alter behavior. These behavioral alterations likely stem from changes in prefrontal cortex neuronal activity, which may depend on the properties and expression of ion channels. Nav1.9 sodium channels conduct a Na + current that is TTX resistant with a low threshold and noninactivating over time. The purpose of this study was to assess the presence of Nav1.9 channels in medial prefrontal cortex (mPFC) layer II and V pyramidal neurons in young (20-day old), late adolescent (60-day old), and adult (6- to 7-month old) rats. First, we demonstrated that layer II and V mPFC pyramidal neurons in slices obtained from young rats exhibited a TTX-resistant, low-threshold, noninactivating, and voltage-dependent Na + current. The mRNA expression of the SCN11a gene (which encodes the Nav1.9 channel) in mPFC tissue was significantly higher in young rats than in late adolescent and adult rats. Nav1.9 protein was immunofluorescently labeled in mPFC cells in slices and analyzed via confocal microscopy. Nav1.9 immunolabeling was present in layer II and V mPFC pyramidal neurons and was more prominent in the neurons of young rats than in the neurons of late adolescent and adult rats. We conclude that Nav1.9 channels are expressed in layer II and V mPFC pyramidal neurons and that Nav1.9 protein expression in the mPFC pyramidal neurons of late adolescent and adult rats is lower than that in the neurons of young rats. © 2017 Wiley Periodicals, Inc. Develop Neurobiol 77: 1371-1384, 2017., (© 2017 Wiley Periodicals, Inc.)

Valproic acid is frequently prescribed and used to treat epilepsy, bipolar disorder and other conditions. However, the mechanism of action of valproic acid has not been fully elucidated. The aim of this study was to assess the influence of valproic acid (200 μM) on TTX-resistant sodium currents in mPFC pyramidal neurons. Valproic acid inhibited the maximal amplitude and did not change the activation parameters of TTX-resistant sodium currents. Moreover, valproic acid (2 μM and 200 μM) shifted the TTX-resistant sodium channel inactivation curve towards hyperpolarisation. In the presence of valproic acid, TTX-resistant sodium currents recovered from inactivation more slowly. Valproic acid did not influence the use-dependent blockade of TTX-resistant sodium currents. This study suggests that a potential new mechanism of the antiepileptic action of valproic acid is, among others, inhibition of TTX-resistant sodium currents., (Copyright © 2017 Elsevier Inc. All rights reserved.)