Ligand-gated mechanisms leading to ictogenesis in focal epileptic disorders.

We review here the neuronal mechanisms that cause seizures in focal epileptic disorders and, specifically, those involving limbic structures that are known to be implicated in human mesial temporal lobe epilepsy. In both epileptic patients and animal models, the initiation of focal seizures - which are most often characterized by a low-voltage fast onset EEG pattern - is presumably dependent on the synchronous firing of GABA-releasing interneurons that, by activating post-synaptic GABAA receptors, cause large increases in extracellular [K+] through the activation of the co-transporter KCC2. A similar mechanism may contribute to seizure maintenance; accordingly, inhibiting KCC2 activity transforms seizure activity into a continuous pattern of short-lasting epileptiform discharges. It has also been found that interactions between different areas of the limbic system modulate seizure occurrence by controlling extracellular [K+] homeostasis. In line with this view, low-frequency electrical or optogenetic activation of limbic networks restrain seizure generation, an effect that may also involve the activation of GABAB receptors and activity-dependent changes in epileptiform synchronization. Overall, these findings highlight the paradoxical role of GABAA signaling in both focal seizure generation and maintenance, emphasize the efficacy of low-frequency activation in abating seizures, and provide experimental evidence explaining the poor efficacy of antiepileptic drugs designed to augment GABAergic function in controlling seizures in focal epileptic disorders.

Paradoxical effects of optogenetic stimulation in mesial temporal lobe epilepsy.

OBJECTIVE: To establish the effects induced by long-term, unilateral stimulation of parvalbumin (PV)-positive interneurons on seizures, interictal spikes, and high-frequency oscillations (80-500Hz) occurring after pilocarpine-induced status epilepticus (SE)-a proven model of mesial temporal lobe epilepsy (MTLE)-in transgenic mice expressing or not expressing ChR2. METHODS: PV-ChR2 (n = 6) and PV-Cre (n = 6) mice were treated with pilocarpine to induce SE. Three hours after SE onset, unilateral optogenetic stimulation (450nm, 25mW, 20-millisecond pulses delivered at 8Hz for 30 seconds every 2 minutes) of CA3 PV-positive interneurons was implemented for 14 continuous days in both groups. RESULTS: Rates of seizures (p < 0.01), interictal spikes (p < 0.001), and interictal spikes with fast ripples (250-500Hz) (p < 0.001) were lower in PV-ChR2 than in PV-Cre mice. Ripples (80-200Hz) occurring outside of interictal spikes had higher rates in the PV-ChR2 group (p < 0.01), whereas isolated fast ripples had lower rates (p < 0.01). However, seizure probability was higher during optogenetic stimulation in PV-ChR2 compared to PV-Cre animals (p < 0.05). INTERPRETATION: Our findings show that the unilateral activation of CA3 PV-positive interneurons exerts anti-ictogenic effects associated with decreased rates of interictal spikes and fast ripples in this MTLE model. However, PV-positive interneuron stimulation can paradoxically trigger seizures in epileptic animals, supporting the notion that γ-aminobutyric acid type A signaling can also initiate ictogenesis. ANN NEUROL 2019;86:714-728.

Optogenetic Low-Frequency Stimulation of Specific Neuronal Populations Abates Ictogenesis.

Despite many advances made in understanding the pathophysiology of epileptic disorders, seizures remain poorly controlled in approximately one-third of patients with mesial temporal lobe epilepsy. Here, we established the efficacy of cell type-specific low-frequency stimulation (LFS) in controlling ictogenesis in the mouse entorhinal cortex (EC) in an in vitro brain slice preparation. Specifically, we used 1 Hz optogenetic stimulation of calcium/calmodulin-dependent protein kinase II-positive principal cells as well as of parvalbumin- or somatostatin-positive interneurons to study the effects of such repetitive activation on epileptiform discharges induced by 4-aminopyridine. We found that 1 Hz stimulation of any of these cell types reduced the frequency and duration of ictal discharges in some trials, while completely blocking them in others. The field responses evoked by the stimulation of each cell type revealed that their duration and amplitude were higher when principal cells were targeted. Furthermore, following a short period of silence ranging from 67 to 135 s, ictal discharges were re-established with similar duration and frequency as before stimulation; however, this period of silence was longer following principal cell stimulation compared with parvalbumin- or somatostatin-positive interneuron stimulation. Our results show that LFS of either excitatory or inhibitory cell networks in EC are effective in controlling ictogenesis. Although optogenetic stimulation of either cell type significantly reduced the occurrence of ictal discharges, principal cell stimulation resulted in a more prolonged suppression of ictogenesis, and, thus, it may constitute a better approach for controlling seizures.SIGNIFICANCE STATEMENT Epilepsy is a neurological disorder characterized by an imbalance between excitation and inhibition leading to seizures. Many epileptic patients do not achieve adequate seizure control using antiepileptic drugs. Low-frequency stimulation (LFS) is an alternative tool for controlling epileptiform activity in these patients. However, despite the temporal and spatial control offered by LFS, such a procedure lacks cell specificity, which may limit its efficacy. Using an optogenetic approach, we report here that LFS of two interneuron subtypes and, even more so, of principal cells can reliably shorten or abolish seizures in vitro Our work suggests that targeted LFS may constitute a reliable means for controlling seizures in patients presenting with focal seizures.

Role of KCC2-dependent potassium efflux in 4-Aminopyridine-induced Epileptiform synchronization.

A balance between excitation and inhibition is necessary to maintain stable brain network dynamics. Traditionally, seizure activity is believed to arise from the breakdown of this delicate balance in favor of excitation with loss of inhibition. Surprisingly, recent experimental evidence suggests that this conventional view may be limited, and that inhibition plays a prominent role in the development of epileptiform synchronization. Here, we explored the role of the KCC2 co-transporter in the onset of inhibitory network-induced seizures. Our experiments in acute mouse brain slices, of either sex, revealed that optogenetic stimulation of either parvalbumin- or somatostatin-expressing interneurons induced ictal discharges in rodent entorhinal cortex during 4-aminopyridine application. These data point to a proconvulsive role of GABAA receptor signaling that is independent of the inhibitory input location (i.e., dendritic vs. somatic). We developed a biophysically realistic network model implementing dynamics of ion concentrations to explore the mechanisms leading to inhibitory network-induced seizures. In agreement with experimental results, we found that stimulation of the inhibitory interneurons induced seizure-like activity in a network with reduced potassium A-current. Our model predicts that interneuron stimulation triggered an increase of interneuron firing, which was accompanied by an increase in the intracellular chloride concentration and a subsequent KCC2-dependent gradual accumulation of the extracellular potassium promoting epileptiform ictal activity. When the KCC2 activity was reduced, stimulation of the interneurons was no longer able to induce ictal events. Overall, our study provides evidence for a proconvulsive role of GABAA receptor signaling that depends on the involvement of the KCC2 co-transporter.

Interictal oscillations and focal epileptic disorders.

Neuronal network oscillations represent a main feature of the brain activity recorded in the EEG under normal and pathological conditions such as epilepsy. Specific oscillations occur between seizures in patients and in animal models of focal epilepsy, and thus, they are termed interictal. According to their shape and intrinsic signal frequency, interictal oscillations are classified as spikes and high-frequency oscillations (HFOs). Interictal spikes are recorded in the 'wideband' EEG signal and consist of large-amplitude events that usually last less than 1 s; HFOs, in contrast, are extracted by amplifying the appropriately filtered EEG signal and are usually categorized as ripples (80-200 Hz) and fast ripples (250-500 Hz). Interictal spikes and HFOs are used in clinical practice to localize the seizure onset zone in focal epileptic disorders, which is fundamental for performing successful surgical interventions in epileptic patients not responding to anti-epileptic drug therapy. Both types of interictal oscillations have been widely studied in animal models of focal epilepsy to identify the mechanisms underlying their generation as well as to establish their role in ictogenesis and epileptogenesis. In this review, we will address the cellular mechanisms underlying the generation of interictal spikes and HFOs in animal models of epileptiform synchronization and of focal epilepsy. Moreover, we will highlight in vitro and in vivo evidence indicating that these interictal oscillations mirror specific, dynamic changes in neuronal network excitability causing seizure generation (i.e. ictogenesis) and leading to a chronic epileptic condition (i.e. epileptogenesis).

Activation of specific neuronal networks leads to different seizure onset types.

OBJECTIVE: Ictal events occurring in temporal lobe epilepsy patients and in experimental models mimicking this neurological disorder can be classified, based on their onset pattern, into low-voltage, fast versus hypersynchronous onset seizures. It has been suggested that the low-voltage, fast onset pattern is mainly contributed by interneuronal (γ-aminobutyric acidergic) signaling, whereas the hypersynchronous onset involves the activation of principal (glutamatergic) cells. METHODS: Here, we tested this hypothesis using the optogenetic control of parvalbumin-positive or somatostatin-positive interneurons and of calmodulin-dependent, protein kinase-positive, principal cells in the mouse entorhinal cortex in the in vitro 4-aminopyridine model of epileptiform synchronization. RESULTS: We found that during 4-aminopyridine application, both spontaneous seizure-like events and those induced by optogenetic activation of interneurons displayed low-voltage, fast onset patterns that were associated with a higher occurrence of ripples than of fast ripples. In contrast, seizures induced by the optogenetic activation of principal cells had a hypersynchronous onset pattern with fast ripple rates that were higher than those of ripples. INTERPRETATION: Our results firmly establish that under a similar experimental condition (ie, bath application of 4-aminopyridine), the initiation of low-voltage, fast and of hypersynchronous onset seizures in the entorhinal cortex depends on the preponderant involvement of interneuronal and principal cell networks, respectively.

Specific imbalance of excitatory/inhibitory signaling establishes seizure onset pattern in temporal lobe epilepsy.

Low-voltage fast (LVF) and hypersynchronous (HYP) patterns are the seizure-onset patterns most frequently observed in intracranial EEG recordings from mesial temporal lobe epilepsy (MTLE) patients. Both patterns also occur in models of MTLE in vivo and in vitro, and these studies have highlighted the predominant involvement of distinct neuronal network/neurotransmitter receptor signaling in each of them. First, LVF-onset seizures in epileptic rodents can originate from several limbic structures, frequently spread, and are associated with high-frequency oscillations in the ripple band (80-200 Hz), whereas HYP onset seizures initiate in the hippocampus and tend to remain focal with predominant fast ripples (250-500 Hz). Second, in vitro intracellular recordings from principal cells in limbic areas indicate that pharmacologically induced seizure-like discharges with LVF onset are initiated by a synchronous inhibitory event or by a hyperpolarizing inhibitory postsynaptic potential barrage; in contrast, HYP onset is associated with a progressive impairment of inhibition and concomitant unrestrained enhancement of excitation. Finally, in vitro optogenetic experiments show that, under comparable experimental conditions (i.e., 4-aminopyridine application), the initiation of LVF- or HYP-onset seizures depends on the preponderant involvement of interneuronal or principal cell networks, respectively. Overall, these data may provide insight to delineate better therapeutic targets in the treatment of patients presenting with MTLE and, perhaps, with other epileptic disorders as well.

Interneuron activity leads to initiation of low-voltage fast-onset seizures.

Seizures in temporal lobe epilepsy can be classified as hypersynchronous and low-voltage fast according to their onset patterns. Experimental evidence suggests that low-voltage fast-onset seizures mainly result from the synchronous activity of γ-aminobutyric acid-releasing cells. In this study, we tested this hypothesis using the optogenetic control of parvalbumin-positive interneurons in the entorhinal cortex, in the in vitro 4-aminopyridine model. We found that both spontaneous and optogenetically induced seizures had similar low-voltage fast-onset patterns. In addition, both types of seizures presented with higher ripple than fast ripple rates. Our data demonstrate the involvement of interneuronal networks in the initiation of low-voltage fast-onset seizures.

Neurosteroidal modulation of in vitro epileptiform activity is enhanced in pilocarpine-treated epileptic rats.

We employed field potential recordings in brain slices obtained from pilocarpine-treated epileptic (4-5weeks following a pilocarpine-induced status epilepticus) and age-matched, non-epileptic control (NEC) rats to establish the effects of the neurosteroid allotetrahydrodeoxycorticosterone (THDOC) on the epileptiform activity - including high frequency oscillations (HFOs; ripples: 80-200Hz, fast ripples: 250-500Hz) - induced by 4-aminopyridine (4AP) in piriform (PC) and entorhinal (EC) cortices. Both structures are highly susceptible to generate seizures and may also be involved in epileptogenesis. We found that THDOC application to pilocarpine-treated slices: (i) decreased interictal discharge frequency in PC while increasing it in EC; (ii) abolished ictal discharges in both areas in approx. one third of the experiments and reduced them in frequency and duration in the remaining experiments; and (iii) increased the occurrence of ripples and fast ripples associated to interictal events, and modified their pattern of occurrence during ictal discharges in both PC and EC. These effects were either weaker or absent in NEC tissue. Our results demonstrate that THDOC plays a structure-dependent modulatory role in epileptiform synchronization in the pilocarpine-treated epileptic rat brain where its actions are more pronounced than in NEC tissue. This evidence supports the application of neurosteroids as potential antiepileptic tools.

Identification of a Novel Homozygous Mutation in PRDM12 Gene in a Patient with Hereditary Sensory and Autonomic Neuropathy Type VIII.

Hereditary sensory autonomic neuropathy type VIII (HSAN-VIII) is a rare genetic disease that occurs due to mutations in the PRDM12 gene. Here, we describe a novel homozygous mutation c.826_840dupTGCAACCGCCGCTTC (p.Cys276_Phe280dup) on exon 5 in the PRDM12 gene identified by WES and confirmed using Sanger sequencing method.

Cryopreserved clinical-grade human embryonic stem cell-derived dopaminergic progenitors function in Parkinson's disease models.

AIM: Parkinson's Disease (PD) is a common age-related neurodegenerative disorder with a rising prevalence. Human pluripotent stem cells have emerged as the most promising source of cells for midbrain dopaminergic (mDA) neuron replacement in PD. This study aimed to generate transplantable mDA progenitors for treatment of PD. MATERIALS AND METHODS: Here, we optimized and fine-tuned a differentiation protocol using a combination of small molecules and growth factors to induce mDA progenitors to comply with good manufacturing practice (GMP) guidelines based on our clinical-grade human embryonic stem cell (hESC) line. KEY FINDINGS: The resulting mDA progenitors demonstrated robust differentiation and functional properties in vitro. Moreover, cryopreserved mDA progenitors were transplanted into 6-hydroxydopamine-lesioned rats, leading to functional recovery. SIGNIFICANCE: We demonstrate that our optimized protocol using a clinical hESC line is suitable for generating clinical-grade mDA progenitors and provides the ground work for future translational applications.

Prevalence of Chromosomal Abnormalities in Iranian Patients with Infertility.

BACKGROUND: The numerical and structural abnormalities of chromosomes are the most common cause of infertility. Here, we evaluated the prevalence and types of chromosomal abnormalities in Iranian infertile patients. METHODS: We enrolled 1750 couples of reproductive age with infertility, who referred to infertility clinics in Tehran during 2014- 2019, in order to perform chromosomal analysis. Peripheral blood samples were obtained from all couples and chromosomal abnormalities were evaluated by G-banded metaphase karyotyping. In some cases, the detected abnormalities were confirmed using fluorescence in-situ hybridization (FISH). RESULTS: We detected various chromosomal abnormalities in 114/3500 (3.257%) patients with infertility. The prevalence of chromosomal abnormalities was 44/114 (38.596%) among infertile females and 70/114 (61.403%) among infertile males. Structural chromosomal abnormalities were found in 27/1750 infertile females and 35/1750 infertile males. Numerical chromosomal abnormalities were found in 17/1750 of females and 35/1750 of males. The 45, XY, rob (13;14) (p10q10) translocation and Klinefelter syndrome (47, XXY) were the most common structural and numerical chromosomal abnormalities in the Iranian infertile patients, respectively. CONCLUSION: In general, we found a high prevalence of chromosomal abnormalities in Iranian patients with reproductive problems. Our study highlights the importance of cytogenetic studies in infertile patients before starting infertility treatments approaches.

Synthetic developmental biology: Engineering approaches to guide multicellular organization.

Multicellular organisms of various complexities self-organize in nature. Organoids are in vitro 3D structures that display important aspects of the anatomy and physiology of their in vivo counterparts and that develop from pluripotent or tissue-specific stem cells through a self-organization process. In this review, we describe the multidisciplinary concept of "synthetic developmental biology" where engineering approaches are employed to guide multicellular organization in an experimental setting. We introduce a novel classification of engineering approaches based on the extent of microenvironmental manipulation applied to organoids. In the final section, we discuss how engineering tools might help overcome current limitations in organoid construction.

Therapeutic potential of pluripotent stem cell-derived dopaminergic progenitors in Parkinson's disease: a systematic review protocol.

BACKGROUND: Parkinson's disease (PD) is the second most common age-dependent neurodegenerative disease that causes motor and cognitive disabilities. This disease is associated with a loss of dopamine content within the putamen, which stems from the degeneration of dopaminergic (DA) neurons in the substantia nigra pars compacta (SNc). Several approved drugs are available that can effectively treat symptoms of PD. However, long-term medical management is often complicated and does not delay or halt disease progression. Alternatively, cell replacement strategies can address these shortcomings and provide dopamine where it is needed. Although using human pluripotent stem cells (hPSCs) for treatment of PD is a promising alternative, no consensus in the literature pertains to efficacy concerns of hPSC-based therapy for PD. This systematic review aims to investigate the efficacy of primate PSC-derived DA progenitor transplantation to treat PD in preclinical studies. METHODS: This is a systematic review of preclinical studies in animal models of PD. We intend to use the following databases as article sources: MEDLINE (via PubMed), Web of Science, and SCOPUS without any restrictions on language or publication status for all related articles published until the end of April 2021. Two independent reviewers will select the titles and abstracts, extract data from qualifying studies, and assess the risk of bias using the SYstematic Review Centre for Laboratory animal Experimentation (SYRCLE) risk of bias tool and the Collaborative Approach to Meta-Analysis and Review of Animal Data from Experimental Studies (CAMARADES) checklist. Apomorphine-induced rotation test (APO-IR) and amphetamine-induced rotation test (AMP-IR) are defined as the primary outcomes. The standardized mean difference (SMD) by Hedges' g method (r) and odds ratio (OR) and related 95% confidence interval (CI) will be calculated to determine the size effect of the treatment. The heterogeneity between studies will be calculated by "I2 inconsistency of values and Cochran's Q statistical test," where I2 > 50% and/or p < 0.10 suggests high heterogeneity. Meta-analyses of random effects will be run when appropriate. DISCUSSION: This study will present an overview of preclinical research on PSCs and their therapeutic effects in PD animal models. This systematic review will point out the strengths and limitations of studies in the current literature while encouraging the funding of new studies by public health managers and governmental bodies.

Identification of a novel homozygous mutation in the DDR2 gene from a patient with spondylo-meta-epiphyseal dysplasia by whole exome sequencing.

OBJECTIVES: The spondylo-meta-epiphyseal dysplasia (SMED) short limbs-hand type is a rare autosomal recessive disease, which is characterized by premature calcification leading to severe disproportionate short stature and various skeletal changes. Defective function of a conserved region encoding discoidin domain receptor tyrosine kinase 2 (DDR2 protein) by the discoidin domain-containing receptor 2 (DDR2 gene) is cause of this disease. The purpose of present study was to investigate disease-causing mutations on DDR2 gene in an Iranian family with SMED, and predict the DDR2 protein molecular mechanism in development of SMED. MATERIALS AND METHODS: In the present study, we evaluated a 2-year-old male with SMED. Detection of genetic changes in the studied patient was performed using Whole-Exome Sequencing (WES). PCR direct sequencing was performed for analysis of co-segregation of variants with the disease in family. Finally, in silico study was performed for further identification of molecular function of the identified genetic variant. RESULTS: We detected a novel splice-site mutation (NM_001014796: exon9: c.855+1G>A; NM_006182: exon8: c.855+1G>A) in DDR2 gene of the studied patient using WES. This mutation was exclusively detected in patients with homozygous SMED, not in healthy people. The effects of detected mutation on functions of DDR2 protein was predicted using in silico study. CONCLUSION: The causative mutation in studied patient with SMED was identified using Next-generation sequencing (NGS), successfully. The identified novel mutation in DDR2 gene can be useful in prenatal diagnosis (PND) of SMED, preimplantation genetic diagnosis (PGD), and genetic counseling.

Optogenetics in the Era of Cerebral Organoids.

The human brain has been deemed the most complex organ and has captivated neuroscientists for decades. Most studies of this organ have relied on reductionist model systems. Although all model systems are essentially wrong, cerebral organoids so far represent the closest recapitulation of human brain development and disease both in terms of cell diversity and organization. The optogenetic technique can be used in this context to study the functional neuroanatomy of the brain, to examine the neural circuits, and to determine the etiology of neurological disorders. In this opinion article, we suggest ways in which optogenetics can be combined with cerebral organoids to allow unprecedented precision and accuracy in studying normal and aberrant neurodevelopmental processes and, as well, neurodegenerative diseases.

High-frequency oscillations and mesial temporal lobe epilepsy.

The interest of epileptologists has recently shifted from the macroscopic analysis of interictal spikes and seizures to the microscopic analysis of short events in the EEG that are not visible to the naked eye but are observed once the signal has been filtered in specific frequency bands. With the use of new technologies that allow multichannel recordings at high sampling rates and the development of computer algorithms that permit the automated analysis of extensive amounts of data, it is now possible to extract high-frequency oscillations (HFOs) between 80 and 500Hz from the EEG; HFOs have been further categorised as ripples (80-200Hz) and fast ripples (250-500Hz). Within the context of epileptic disorders, HFOs should reflect the pathological activity of neural networks that sustain seizure generation, and could serve as biomarkers of epileptogenesis and ictogenesis. We review here the presumptive cellular mechanisms of ripples and fast ripples in mesial temporal lobe epilepsy. We also focus on recent findings regarding the occurrence of HFOs during epileptiform activity observed in in vitro models of epileptiform synchronization, in in vivo models of mesial temporal lobe epilepsy and in epileptic patients. Finally, we address the effects of anti-epileptic drugs on HFOs and raise some questions and issues related to the definition of HFOs.

Anti-inflammatory activity of Elaeagnus angustifolia fruit extract on rat paw edema.

BACKGROUND: The Elaeagnus angustifolia fruit has been traditionally used in Iranian herbal medicine to treat diarrhea and rheumatoid arthritis. In the present study, the effects of E. angustifolia fruit extract on the acute and chronic phases of formalin-induced rat paw edema were examined. METHODS: The acute and chronic anti-inflammatory effects of E. angustifolia fruit extract were investigated through the subcutaneous injection of 100 µL of formalin (2.5%) into a rat's hind paw. Thirty minutes before the procedure, the experimental groups were treated intraperitoneally with hydroalcoholic fruit extracts of E. angustifolia (concentrations of 100, 300, 700, and 1000 mg/kg); sodium salicylate (SS, 400 mg/kg) and distilled water were used as positive and negative control groups, respectively. Treatment with SS and the fruit extracts were performed daily for 8 days, and the degree of edema was measured by using mercury plethysmometer and digital caliper. RESULTS: In the acute anti-inflammatory study, the extract showed a significant anti-inflammatory effect in a dose-dependent manner. The results of 1000 mg/kg of the extract was significantly different compared with the negative control group (p<0.05) and was comparable to sodium salicylate (p<0.05). Results from the chronic study suggested that E. angustifolia extract significantly reduced paw edema and inflammation in a dose-dependent manner. The results also showed that the measurement by digital caliper and mercury plethysmometer were both reliable and might be applied interchangeably (p<0.01). Phytochemical tests indicated that the hydroalcoholic fruit extract of E. angustifolia was positive for cardiac glycosides, flavonoids, terpenoids, and saponins. CONCLUSIONS: Based on our findings, the E. angustifolia fruit extract probably has acute and chronic anti-inflammatory activities to support its applications in folk medicine.

Limbic networks and epileptiform synchronization: the view from the experimental side.

In this review, we summarize findings obtained in acute and chronic epilepsy models and in particular experiments that have revealed how neuronal networks in the limbic system-which is closely involved in the pathophysiogenesis of mesial temporal lobe epilepsy (MTLE)-produce hypersynchronous discharges. MTLE is often associated with a typical pattern of brain damage known as mesial temporal sclerosis, and it is one of the most refractory forms of partial epilepsy in adults. Specifically, we will address the cellular and pharmacological features of abnormal electrographic events that, as in MTLE patients, can occur in in vivo and in vitro animal models; these include interictal and ictal discharges along with high-frequency oscillations. In addition, we will consider how different limbic structures made hyperexcitable by acute pharmacological manipulations interact during epileptiform discharge generation. We will also review the electrographic characteristics of two types of seizure onsets that are most commonly seen in human and experimental MTLE as well as in in vitro models of epileptiform synchronization. Finally, we will address the role played by neurosteroids in reducing epileptiform synchronization and in modulating epileptogenesis.