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Low-frequency electrical stimulation is used to treat some drug-resistant forms of epilepsy. Despite the effectiveness of the method in suppressing seizures, there is a considerable risk of side effects. An optogenetic approach allows the targeting of specific populations of neurons, which can increase the effectiveness and safety of low-frequency stimulation. In our study, we tested the efficacy of the suppression of ictal activity in entorhinal cortex slices in a 4-aminopyridine model with three variants of low-frequency light stimulation (LFLS): (1) activation of excitatory and inhibitory neurons (on Thy1-ChR2-YFP mice), (2) activation of inhibitory interneurons only (on PV-Cre mice after virus injection with channelrhodopsin2 gene), and (3) hyperpolarization of excitatory neurons (on Wistar rats after virus injection with archaerhodopsin gene). Only in the first variant did simultaneous LFLS of excitatory and inhibitory neurons replace ictal activity with interictal activity. We suggest that LFLS caused changes in the concentration gradients of K+ and Na+ cations across the neuron membrane, which activated Na-K pumping. According to the mathematical modeling, the increase in Na-K pump activity in neurons induced by LFLS led to an antiepileptic effect. Thus, a less specific and generalized optogenetic effect on entorhinal cortex neurons was more effective in suppressing ictal activity in the 4-aminopyridine model.

Data on the long-term consequences of a single episode of generalized seizures in infants are inconsistent. In this study, we examined the effects of pentylenetetrazole-induced generalized seizures in three-week-old rats. One month after the seizures, we detected a moderate neuronal loss in several hippocampal regions: CA1, CA3, and hilus, but not in the dentate gyrus. In addition, long-term synaptic potentiation (LTP) was impaired. We also found that the mechanism of plasticity induction was altered: additional activation of metabotropic glutamate receptors (mGluR1) is required for LTP induction in experimental rats. This disturbance of the plasticity induction mechanism is likely due to the greater involvement of perisynaptic NMDA receptors compared to receptors located in the core part of the postsynaptic density. This hypothesis is supported by experiments with selective blockades of core-located NMDA receptors by the use-dependent blocker MK-801. MK-801 had no effect on LTP induction in experimental rats and suppressed LTP in control animals. The weakening of the function of core-located NMDA receptors may be due to the disturbed clearance of glutamate from the synaptic cleft since the distribution of the astrocytic glutamate transporter EAAT2 in experimental animals was found to be altered.

Acute seizures can severely affect brain function and development. However, the underlying pathophysiological mechanisms are still poorly understood. Disturbances of the glutamatergic system are considered one of the critical mechanisms of neurological abnormalities. In the present study, we analyzed changes in the expression of NMDA and AMPA receptor subunits in the different brain regions (dorsal hippocampus, amygdala, and the medial prefrontal, temporal, and entorhinal cortex) using a pentylenetetrazole (PTZ) model of seizures in 3-week-old rats. A distinctive feature of this model is that the administration of PTZ causes severe acute seizures, which are not followed by the development of spontaneous recurrent seizures later on. Subunit expression was analyzed using qRT-PCR and Western blotting during the first week after seizures. The most pronounced alterations of mRNA and protein levels were observed in the dorsal hippocampus. We found decreased expression of the GluA2 mRNA 7 days after seizures (PSE7), as well as reduced GluN2a protein levels on PSE7. Significant alterations in the expression of different receptor subunits in the mRNA but not protein levels were observed in the entorhinal cortex and amygdala. In contrast, in the medial prefrontal and temporal cortex, we found almost no changes in the expression of the studied genes. The identified changes deepen our understanding of post-seizure disturbances in the developing brain and confirm that although various brain structures are involved in seizures, the hippocampus is the most vulnerable.

Epilepsy is characterized by repeated sudden-onset epileptic seizures. Around 30% of cases of epilepsy show drug resistance, with the result that the disease can progress and lead to degradation of cognitive capacities and the onset of concomitant psychoneurological diseases. Early therapeutic interventions can reduce disease severity, while suppression of epileptogenesis is regarded as the most promising strategy for preventing the development of epilepsy after disease-provoking events. NMDA receptors are regarded as a potential target for suppressing epileptogenesis. Impairment to NMDA receptor function occurs at all stages of the development of epilepsy. Changes in their expression are seen in the fi rst hours after acute seizures, while NMDA receptors themselves are actively involved in generating epileptic activity. In addition, NMDA receptor antagonists effectively suppress epileptiform activity in a variety of models of convulsive states and status epilepticus. This review considers existing data on the role played by NMDA receptors in the development of epilepsy and how their expression changes at different periods of epileptogenesis, and the potential use of NMDA receptor antagonists and modulators in preventing epileptogenesis is discussed.

In this work, we studied the effect of doping with d metals (Me: Mn, Fe, Cu) on the photocatalytic activity and optical properties of the hetero-structured, bismuth-containing Sr1-xMexBi4O7 / (BiO)2CO3 photo-catalyst, where x = 0.01–0.05. The stages of oxidative pyrolysis of precursor organometallic complexes with sorbitol by differential scanning calorimetry have been studied. The first stage of oxidative destruction is induced by the influence of nitrate-ion and terminates at temperatures below . The second stage of pyrolysis is associated with a further thermal degradation of sorbitol to pyrolytic carbon in the temperature range 113 - . The third stage 287–462°C is associated with the combustion of the formed pyrolytic carbon. The final stage of pyrolysis occurs in the temperature range of 462-with the formation of the target synthesis products. It has been established that Cu is the most effective dopant. In contrast to other metals, doping with copper results in the formation of a solid solution in the CuO-SrBi4O7 system. Compared to the initial SrBi4O7, as a result of doping Cu in an amount of 5 at. % the largest change in the band gap from 2.77 to 2.62 eV is achieved. The efficiency of photo-catalysis (estimated by the half-conversion of methylene blue) of the Cu0.05Sr0.95Bi4O7 / (BiO) 2CO3 composition turned out to be 2.3 times higher than the initial - undoped catalyst; and 3.1 times higher than in the non-catalytic process.

A study was carried out to obtain effective photocatalytic coatings on a ceramic silicate carrier. The analysis of the characteristics of silicate materials, such as: ceramic carrier "Biopur"; porous glass carrier "Siporax"; glass-ceramic carrier (sitall) "Biopur forte" produced by the company "SERA", Germany, was made. According to X-ray phase analysis data, it was shown that the “Biopur” ceramic support is formed by magnesium aluminosilicates of the composition MgAl2Si3O10 and MgAl2Si4O12. The porous material “Siporax” is X-ray amorphous. The silicate material “Biopur forte” does not have a pronounced amorphous component in its structure and can be assigned to the class of sitall with a high SiO2 content and a low content of alkali and alkaline earth metal cations in the structure. A method for impregnating a ceramic support with a solution of a bismuth photo-catalyst precursor, a specially developed composition of a complex of bismuth with sorbitol, is considered. An effective concentration of a solution of a complex of bismuth with sorbitol in ethanol equal to 10% was found. By low-temperature pyrolysis at , photo-catalytically active coatings of strontium bismuthates were obtained on each of the considered types of ceramic supports. The highest photocatalytic activity was detected in the coating deposited on a ceramic carrier with a glass structure – “Biopur forte”. A study of the photocatalytic activity of coatings, based on strontium bismuthate, depending on the multiplicity of coating on a “Biopur forte” ceramic carrier, was made. The effective number of layers of the photocatalytic coating on a “Biopur forte” ceramic carrier is determined, which corresponds to the highest rate of decrease in the optical density of a model organic pollutant upon irradiation with visible light in the spectrum.

Children are more likely to develop epileptic seizures (ictal discharges lasting tens of seconds) than adults. A higher predisposition of the juvenile brain to the generation of epileptiform activity is thought to be due to a prevalence of inhibition over excitation at the early stage of brain development. However, the molecular and physiological mechanisms underlying these age-related differences are yet to be clarified. We compared the ictal activity induced by a convulsant 4-aminopyridine (4-AP) in the horizontal slices of the entorhinal cortex and hippocampus of 3- and 8-week-old Wistar rats. In 3-week-old rats, the ictal discharge was always preceded by a detectable preictal activity, as manifested in one or several 3–4-s GABA-glutamate events, whereas in 8-week-old rats, such events were typically absent or very rare (no more than one occasional short event). The ictal activity resistance to external exposures was also age-dependent. In 8-week-old rats, by contrast to 3-week-old animals, ictal discharge generation in the entorhinal cortex was blocked completely and replaced by 0.2–0.3 Hz interictal activity (simultaneous 1–3-s burst discharges) by a partial blockade of KCC2 cotransporter or Na+–K+-pump, as well as by low-frequency electric stimulation. Thus, our data indicate that ictal discharges in the immature (3-week-old) brain are more resistant to external exposures than in the brain of adult rats. Interictal and ictal epileptiform activities are antagonistic in 8-week-old animals. In contrast, the appearance of interictal activity interrupts the generation of ictal discharges completely. It can therefore be considered as one of the putative antiepileptic mechanisms in the mature rat brain.

Prolonged neonatal febrile seizures (FSs) often lead to cognitive decline and increased risk of psychopathology in adulthood. However, the neurobiological mechanisms underlying the long-term adverse effects of FSs remain unclear. In this study, we exposed rat pups to hyperthermia and induced FSs lasting at least 15 min. We investigated the short-term (one day) and delayed (11–13 and 41–45 days) effects of FSs on some parameters of morphological and functional maturation in the hippocampus. We noticed that FSs altered the developmental pattern of glial fibrillary acidic protein (GFAP) immunoreactivity. In rats aged 21–23 days, GFAP-positive astrocytes covered a smaller area, and their morphological characteristics resembled those of rats at 11 days of age. In post-FS rats, the magnitude of long-term synaptic potentiation was reduced compared to control animals of the same age. Applying the gliotransmitter D-serine, an agonist of the glycine site of NMDA receptors, restored LTP to control values. A decrease in LTP amplitude was correlated with impaired spatial learning and memory in the Barnes maze task in post-FS rats. Our data suggest that impaired neuron–glia interactions may be an essential mechanism of the adverse effects of FS on the developing brain.

Infections in childhood play an essential role in the pathogenesis of cognitive and psycho-emotional disorders. One of the possible mechanisms of these impairments is changes in the functional properties of NMDA and AMPA glutamate receptors in the brain. We suggest that bacterial infections during the early life period, which is critical for excitatory synapse maturation, can affect the subunit composition of NMDA and AMPA receptors. In the present study, we investigated the effect of repetitive lipopolysaccharide (LPS) intraperitoneal (i.p.) administration (25 μg/kg/day on P14, 16, and 18), mimicking an infectious disease, on the expression of subunits of NMDA and AMPA receptors in young rats. We revealed a substantial decrease of GluN2B subunit expression in the hippocampus at P23 using Western blot analysis and real-time polymerase chain reaction assay. Moderate changes were also found in GluN1, GluN2A, and GluA1 mRNA expression. The LPS-treated rats exhibited decreased exploratory and locomotor activity in the open field test and the impairment of spatial learning in the Morris water maze. Behavioral impairments were accompanied by a significant reduction in long-term hippocampal synaptic potentiation. Our data indicate that LPS-treatment in the critical period for excitatory synapse maturation alters ionotropic glutamate receptor gene expression, disturbs synaptic plasticity, and alters behavior.

Epilepsy is one of the most prevalent and devastating neurological disorders characterized by episodes of unusual sensations, loss of awareness, and reoccurring seizures. The frequency and intensity of epileptic fits can vary to a great degree, with almost a third of all cases resistant to available therapies. At present, there is a major unmet need for effective and specific therapeutic intervention. Impairments of the exquisite balance between excitatory and inhibitory synaptic processes in the brain are considered key in the onset and pathophysiology of the disease. As the primary excitatory neurotransmitter in the central nervous system, glutamate has been implicated in the process, with the glutamatergic system holding center stage in the pathobiology as well as in developing disease-modifying therapies. Emerging data pinpoint impairments of glutamate clearance as one of the key causative factors in drug-resistant disease forms. Reinstatement of glutamate homeostasis using pharmacological and genetic modulation of glutamate clearance is therefore considered to be of major translational relevance. In this article, we review the neurobiological and clinical evidence suggesting complex aberrations in the activity and functions of excitatory amino acid transporters (EAATs) in epilepsy, with knock-on effects on glutamate homeostasis as a leading cause for the development of refractory forms. We consider the emerging data on pharmacological and genetic manipulations of EAATs, with reference to seizures and glutamate dyshomeostasis, and review their fundamental and translational relevance. We discuss the most recent advances in the EAATs research in human and animal models, along with numerous questions that remain open for debate and critical appraisal. Contrary to the widely held view on EAATs as a promising therapeutic target for management of refractory epilepsy as well as other neurological and psychiatric conditions related to glutamatergic hyperactivity and glutamate-induced cytotoxicity, we stress that the true relevance of EAAT2 as a target for medical intervention remains to be fully appreciated and verified. Despite decades of research, the emerging properties and functional characteristics of glutamate transporters and their relationship with neurophysiological and behavioral correlates of epilepsy challenge the current perception of this disease and fit unambiguously in neither EAATs functional deficit nor in reversal models. We stress the pressing need for new approaches and models for research and restoration of the physiological activity of glutamate transporters and synaptic transmission to achieve much needed therapeutic effects. The complex mechanism of EAATs regulation by multiple factors, including changes in the electrochemical environment and ionic gradients related to epileptic hyperactivity, impose major therapeutic challenges. As a final note, we consider the evolving views and present a cautious perspective on the key areas of future progress in the field towards better management and treatment of refractory disease forms.

Low-frequency electrical stimulation (LFES) of the brain is one of the promising methods for helping patients with pharmacoresistant epilepsy. However, the mechanism of the antiepileptic effect of LFES is still unclear. We applied electrophysiological and pharmacological tools and mathematical modeling to investigate it. Using the 4-aminopyridine (4-AP) model of epileptiform activity in juvenile rat brain slices, we found that LFES increased the interval between ictal discharges (IDs) in the entorhinal cortex. The blockade of GABAA, GABAB, AMPA, or NMDA synaptic receptors strongly affected the characteristics of epileptiform discharges in slices. However, only under the blockade of GABAB receptors, LFES becomes entirely ineffective, indicating that the activation of GABAB receptors underlies the main LFES antiepileptic effect. Further experiments allowed us to suggest that LFES activates mostly presynaptic GABAB receptors, which decrease the probability of glutamate release. In line with this hypothesis is the following data: 1) LFES reduces the short-term synaptic depression of excitatory postsynaptic currents similar to the agonist of GABAB receptors SKF-97541; 2) the blockade of excitatory amino acid transporters diminishes the antiepileptic effect of LFES; 3) modeling of the effects of LFES on the probability of glutamate release with a previously proposed mathematical model of epileptiform activity Epileptor-2 also shows the increase of the interval between IDs. Our findings point out a crucial role of presynaptic GABAB receptors in the antiepileptic effect of LFES in the 4-AP model in juvenile rat brain slices.

Epilepsy is one of the commonest neurological diseases, though convulsive seizures cannot be completely cured in 30% of patients, such that there is a need to develop new pharmacological approaches to its treatment. In some pathological states, including drug-resistant forms of epilepsy, the mechanisms removing glutamate from the synaptic cleft may be impaired, so one potential approach to these pathological states may be associated with actions on glutamate transporters. The present review analyzes contemporary data on changes in the expression of excitatory amino acid transporter proteins (EAAT) in human epilepsy and in animal models of convulsive states and epilepsy. Mechanisms of actions on the expression and activity of transporters as potential therapeutic targets for the treatment of convulsive states are considered, special attention being paid to analysis of the use of the antibiotic ceftriaxone, which increases the expression and activity of EAAT-2.

Epileptiform activity in living brain slices is the result of the complex integration of excitatory and inhibitory synaptic signals. The time pattern of activation of different synaptic conductances during interictal discharges provides a description of the patterns of operation of neural networks in epileptiform states and a route to analysis of the effects of different pharmacological agents on it. Existing methods of assessing synaptic conductances generally make the assumption that the voltage-current relationships (VCR) of neuron responses are linear and provide for assessment of the contributions of two types of conductance to the postsynaptic response, i.e., excitatory and inhibitory, without discriminating the contributions of specific types of synaptic receptors. We describe here the theoretical basis of a method for simultaneous assessment of the postsynaptic conductances of three types of ionotropic receptors (AMPA NMDA, and GABAA), which undergo activation during interictal discharges in the entorhinal cortex. The proposed algorithm utilizes the different types of VCR of these receptors to assess their contributions to the postsynaptic responses of a neuron and proposes use of the patch clamp method in the whole cell configuration in voltage clamping mode. Use of this method was demonstrated using various models of epileptiform activity as examples. The time courses of synaptic conductances during interictal discharges generated with full preservation of GABAA receptor-mediated conductance were compared using the antibiotic cefepime or bicuculline. Despite the fact that cefepime is a GABAA receptor antagonist, total conductance at the late stages of the interictal discharge was significantly greater as compared with a model in which this type of receptor was not blocked or on use of another competitive antagonist, bicuculline. Thus, the method proposed here identifies fine differences in the time courses of three types of synaptic conductance and allows differences in the proepileptic effects of GABAA receptor blockers to be demonstrated

Potassium ion channels are extensively involved in the regulation of epileptic seizures. The small conductance calcium-sensitive potassium channels (SK channels) and ATP-sensitive potassium (K

Epilepsy is a challenging brain disorder that is often difficult to treat with conventional therapies. The gut microbiota has been shown to play an important role in the development of neuropsychiatric disorders, including epilepsy. In this study, the effects of Bifidobacterium longum, a probiotic, on inflammation, neuronal degeneration, and behavior are evaluated in a lithium–pilocarpine model of temporal lobe epilepsy (TLE) induced in young adult rats. B. longum was administered orally at a dose of 109 CFU/rat for 30 days after pilocarpine injection. The results show that B. longum treatment has beneficial effects on the TLE-induced changes in anxiety levels, neuronal death in the amygdala, and body weight recovery. In addition, B. longum increased the expression of anti-inflammatory and neuroprotective genes, such as Il1rn and Pparg. However, the probiotic had little effect on TLE-induced astrogliosis and microgliosis and did not reduce neuronal death in the hippocampus and temporal cortex. The study suggests that B. longum may have a beneficial effect on TLE and may provide valuable insights into the role of gut bacteria in epileptogenesis. In addition, the results show that B. longum may be a promising drug for the comprehensive treatment of epilepsy.

Status epilepticus (SE) causes persistent abnormalities in the functioning of neuronal networks, often resulting in worsening epileptic seizures. Many details of cellular and molecular mechanisms of seizure-induced changes are still unknown. The lithium–pilocarpine model of epilepsy in rats reproduces many features of human temporal lobe epilepsy. In this work, using the lithium–pilocarpine model in three-week-old rats, we examined the morphological and electrophysiological changes in the hippocampus within a week following pilocarpine-induced seizures. We found that almost a third of the neurons in the hippocampus and dentate gyrus died on the first day, but this was not accompanied by impaired synaptic plasticity at that time. A diminished long-term potentiation (LTP) was observed following three days, and the negative effect of SE on plasticity increased one week later, being accompanied by astrogliosis. The attenuation of LTP was caused by the weakening of N-methyl-D-aspartate receptor (NMDAR)-dependent signaling. NMDAR-current was more than two-fold weaker during high-frequency stimulation in the post-SE rats than in the control group. Application of glial transmitter D-serine, a coagonist of NMDARs, allows the enhancement of the NMDAR-dependent current and the restoration of LTP. These results suggest that the disorder of neuron–astrocyte interactions plays a critical role in the impairment of synaptic plasticity.

Epileptic activity leads to rapid insertion of calcium-permeable α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors (CP-AMPARs) into the synapses of cortical and hippocampal glutamatergic neurons, which generally do not express them. The physiological significance of this process is not yet fully understood, however, it is usually assumed to be a pathological process that augments epileptic activity. Using whole-cell patch-clamp recordings in rat entorhinal cortex slices, we demonstrate that the timing of epileptiform discharges, induced by 4-aminopyridine and gabazine, is determined by the shunting effect of Ca2+-dependent slow conductance, mediated predominantly by K+-channels. The blockade of CP-AMPARs by IEM-1460 eliminates this extra conductance and consequently increases the rate of discharge generation. The blockade of NMDARs reduced the additional conductance to a lesser extent than the blockade of CP-AMPARs, indicating that CP-AMPARs are a more significant source of intracellular Ca2+. The study’s main findings were implemented in a mathematical model, which reproduces the shunting effect of activity-dependent conductance on the generation of discharges. The obtained results suggest that the expression of CP-AMPARs in principal neurons reduces the discharge generation rate and may be considered as a protective mechanism.

Chronic experiments on Wistar and Krushinskii–Molodkina rats, which have an inherited predisposition to audiogenic convulsions, addressed the effects of preliminary administration of memantine and IEM-1921 – NMDA glutamate receptor channel blockers – on brain electrical activity on development of status epilepticus (SE) induced by pilocarpine. Electrograms were recorded from the hippocampus, caudate nucleus, and the somatosensory, visual, and auditory areas of the cortex. The nature and sequence of changes in the phases of SE identifi ed from electrogram patterns were not altered by blockers. In addition, the latent period of the onset of epileptiform activity on the EEG after administration of pilocarpine to Wistar rats decreased almost two-fold (to 10–15 min) after administration of memantine (5 mg/kg) or IEM-1921 (5 mg/kg). In Krushinskii–Molodkina rats, the latent period of development of epileptiform activity was initially shorter (13 ± 2 min) and was not altered by use of blockers. The mean durations of SE after administration of memantine to Wistar and Krushinskii–Molodkina rats were 2 and 3 times, respectively, shorter than without blocker, while durations were reduced seven-fold by IEM-1921. NMDA receptor blockers also signifi cantly weakened behavioral motor convulsions, decreasing the intensity of convulsions from 8 to 4 points on the Pinel and Rovner [1978] scale. These data provide evidence that blockade of NMDA receptors did not prevent the typical development of pilocarpine-induced SE, though duration was signifi cantly reduced.

About one per cent of the world’s population suffers from epilepsy, and approximately 30% of cases fail to respond to medication. Novel approaches to treatment are required to help patients with drug-resistant epilepsy. One potential method consists of low-frequency stimulation of brain structures. However, at this time the mechanism of the anticonvulsant action of low-frequency stimulation is not completely understood. There are significant drawbacks to this method: it is invasive in nature and has nonspecific actions on brain tissues, which leads to various side effects. The development of optogenetics has provided a new impulse to studies of the mechanisms of action of low-frequency stimulation on epileptic activity. In addition, there is hope for significant reductions in the side effects of stimulation, as there is potential for selective activation or, conversely, inhibition of particular neuron populations. This review describes current progress in studies of the mechanisms of the generation and suppression of epileptic activity using an optogenetic method in in vitro and in vivo models of epilepsy. The potentials of this approach for clinical use are discussed.

Effects of 5-HT1 and 5-HT2 receptor agonists and antagonists on membrane properties of motoneurons in the isolated lumbar segment of the frog spinal cord were investigated using intracellular recordings. Application of a 5-HT2A,B,C receptor agonist α-Me-5-HT evoked depolarization of the motoneuronal membrane. The co-application of α-Me-5-HT and a specific 5-HT2B receptor antagonist SB 206553 did not result in depolarization. α-Me-5-HT reduced the amplitude of medium afterhyperpolarization and increased the number of antidromic action potentials (APs). The application of an antagonist SB 206553 abolished these effects. A 5-HT1A/7 receptor agonist 8-OH-DPAT had a time-dependent effect on the number of antidromic APs, evoking an initial short-term excitation followed by an inhibition. The data obtained in our experiments indicate the presence of 5-HT1A/7 and 5-HT2B,C receptors on the postsynaptic membrane of motoneurons. We suggest a possible co-modulation of the accommodative properties of motoneurons by the two types of serotonin receptors, 5-HT2B,C and 5-HT1A.

When studying a preparation of the isolated spinal cord segment of an adult frog, damaged and intact lumbar motoneurons were found to differ significantly in the membrane potential, input resistance and the action potential properties (amplitude, duration, fast and medium phases of the afterhyperpolarization, and the frequency of spikes). Serotonin (5-HT) reduced the amplitude of afterpolarization and increased the frequency of the spikes of the intact neurons, while in the damaged motoneurons, 5-HT increased the amplitude of afterpolarization and had no effect on the frequency of discharges.

Disrupted glutamate clearance in the synaptic cleft leads to synaptic dysfunction and neurological diseases. Decreased glutamate removal from the synaptic cleft is known to cause excitotoxicity. Data on the physiological effects of increased glutamate clearance are contradictory. This study investigated the consequences of ceftriaxone (CTX), an enhancer of glutamate transporter 1 expression, treatment on long-term synaptic potentiation (LTP) in the hippocampus of young rats. In this study, 5-day administration of CTX (200 mg/kg) significantly weakened LTP in CA3-CA1 synapses. As shown by electrophysiological recordings, LTP attenuation was associated with weakening of N-Methyl-D-aspartate receptor (NMDAR)-dependent signaling in synapses. However, PCR analysis did not show downregulation of NMDAR subunits or changes in the expression of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR) subunits. We assume that extracellular burst stimulation activates fewer synapses in CTX-treated animals because increased glutamate reuptake results in reduced spillover, and neighboring synapses do not participate in neurotransmission. Attenuation of LTP was not accompanied by noticeable behavioral changes in the CTX group, with no behavioral abnormalities observed in the open field test or Morris water maze test. Thus, our experiments show that increased glutamate clearance can impair long-term synaptic plasticity and that this phenomenon can be considered a potential side effect of CTX treatment.

Febrile seizures (FSs) in early life are significant risk factors of neurological disorders and cognitive impairment in later life. However, existing data about the impact of FSs on the developing brain are conflicting. We aimed to investigate morphological and functional changes in the hippocampus of young rats exposed to hyperthermia-induced seizures at postnatal day 10. We found that FSs led to a slight morphological disturbance. The cell numbers decreased by 10% in the CA1 and hilus but did not reduce in the CA3 or dentate gyrus areas. In contrast, functional impairments were robust. Long-term potentiation (LTP) in CA3-CA1 synapses was strongly reduced, which we attribute to the insufficient activity of N-methyl-D-aspartate receptors (NMDARs). Using whole-cell recordings, we found higher desensitization of NMDAR currents in the FS group. Since the desensitization of NMDARs depends on subunit composition, we analyzed NMDAR current decays and gene expression of subunits, which revealed no differences between control and FS rats. We suggest that an increased desensitization is due to insufficient activation of the glycine site of NMDARs, as the application of D-serine, the glycine site agonist, allows the restoration of LTP to a control value. Our results reveal a new molecular mechanism of FS impact on the developing brain.

Adenosine deaminase-dependent RNA editing is a widespread universal mechanism of posttranscriptional gene function modulation. Changes in RNA editing level may contribute to various physiological and pathological processes. In the α-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) glutamate receptor GluA2 subunit, A-I editing in the Q607R site leads to dramatic changes in function, making the receptor channel calcium-impermeable. A standard approach for quantifying (un)edited RNAs is based on endpoint PCR (Sanger sequencing or restriction analysis), a time-consuming and semiquantitative method. We aimed to develop RT-qPCR assays to quantify rat Q607R (A-I) edited/unedited mRNA in samples in the present work. Based on self-probing PCR detection chemistry, described initially for detecting short DNA fragments, we designed and optimised RT-qPCR assays to quantify Q607R (un)edited mRNA. We used self-probing primer PCR technology for mRNA quantification for the first time. Using a novel assay, we confirmed that Q607R GluA2 mRNA editing was increased in 14-day- (P14) or 21-day-old (P21) postnatal brain tissue (hippocampus) compared to the embryonic brain (whole brains at E20) in Wistar rats. Q607R unedited GluA2 mRNA was detectable by our assay in the cDNA of mature brain tissue compared to that derived through classical methods. Thus, self-probing primer PCR detection chemistry is an easy-to-use approach for RT-qPCR analysis of RNA editing.

Epilepsy is one of the most prevalent and devastating neurological disorders characterized by episodes of unusual sensations, loss of awareness, and reoccurring seizures. The frequency and intensity of epileptic fits can vary to a great degree, with almost a third of all cases resistant to available therapies. At present, there is a major unmet need for effective and specific therapeutic intervention. Impairments of the exquisite balance between excitatory and inhibitory synaptic processes in the brain are considered key in the onset and pathophysiology of the disease. As the primary excitatory neurotransmitter in the central nervous system, glutamate has been implicated in the process, with the glutamatergic system holding center stage in the pathobiology as well as in developing disease-modifying therapies. Emerging data pinpoint impairments of glutamate clearance as one of the key causative factors in drug-resistant disease forms. Reinstatement of glutamate homeostasis using pharmacological and genetic modulation of glutamate clearance is therefore considered to be of major translational relevance. In this article, we review the neurobiological and clinical evidence suggesting complex aberrations in the activity and functions of excitatory amino acid transporters (EAATs) in epilepsy, with knock-on effects on glutamate homeostasis as a leading cause for the development of refractory forms. We consider the emerging data on pharmacological and genetic manipulations of EAATs, with reference to seizures and glutamate dyshomeostasis, and review their fundamental and translational relevance. We discuss the most recent advances in the EAATs research in human and animal models, along with numerous questions that remain open for debate and critical appraisal. Contrary to the widely held view on EAATs as a promising therapeutic target for management of refractory epilepsy as well as other neurological and psychiatric conditions related to glutamatergic hyperactivity and glutamate-induced cytotoxicity, we stress that the true relevance of EAAT2 as a target for medical intervention remains to be fully appreciated and verified. Despite decades of research, the emerging properties and functional characteristics of glutamate transporters and their relationship with neurophysiological and behavioral correlates of epilepsy challenge the current perception of this disease and fit unambiguously in neither EAATs functional deficit nor in reversal models. We stress the pressing need for new approaches and models for research and restoration of the physiological activity of glutamate transporters and synaptic transmission to achieve much needed therapeutic effects. The complex mechanism of EAATs regulation by multiple factors, including changes in the electrochemical environment and ionic gradients related to epileptic hyperactivity, impose major therapeutic challenges. As a final note, we consider the evolving views and present a cautious perspective on the key areas of future progress in the field towards better management and treatment of refractory disease forms.