2-Deoxy-d-glucose reduces epileptiform activity by presynaptic mechanisms

2-Deoxy-d-glucose (2DG), a glucose analog that inhibits glycolysis, has acute and chronic antiepileptic effects. We evaluated 2DG’s acute effects on synaptic and membrane properties of CA3 pyramidal neurons in vitro. 2DG (10 mM) had no effects on spontaneously occurring postsynaptic currents (PSCs) in 3.5 mM extracellular potassium concentration ([K+]o). In 7.5 mM [K+]o, 2DG significantly reduced the frequency of epileptiform bursting and the charge carried by postsynaptic currents (PSCs) with a greater effect on inward excitatory compared with outward inhibitory charge (71% vs. 40%). In 7.5 mM [K+]o and bicuculline, 2DG reduced significantly the excitatory charge by 67% and decreased the frequency but not amplitude of excitatory PSCs between bursts. In 7.5 mM [K+]o, 2DG reduced pharmacologically isolated inhibitory PSC frequency without a change in amplitude. The frequency but not amplitude of inward miniature PSCs was reduced when 2DG was applied in 7.5 mM [K+]o before bath application of TTX, but there was no effect when 2DG was applied after TTX, indicating a use-dependent uptake of 2DG was required for its actions at a presynaptic locus. 2DG did not alter membrane properties of CA3 neurons except for reducing the slow afterhyperpolarization in 3.5 but not 7.5 mM [K+]o. The reduction in frequency of spontaneous and inward miniature PSCs in elevated [K+]o indicates a presynaptic mechanism of action. 2DG effects required use-dependent uptake and suggest an important role for glycolysis in neuronal metabolism and energetics in states of high neural activity as occur during abnormal network synchronization and seizures. NEW & NOTEWORTHY 2-Deoxy-d-glucose (2DG) is a glycolytic inhibitor and suppresses epileptiform activity acutely and has chronic antiepileptic effects. The mechanisms of the acute effects are not well delineated. In this study, we show 2DG suppressed abnormal network epileptiform activity without effecting normal synaptic network activity or membrane properties. The effects appear to be use dependent and have a presynaptic locus of action. Inhibition of glycolysis is a novel presynaptic mechanism to limit abnormal neuronal network activity and seizures.

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Calcium-Activated Afterhyperpolarizations Regulate Synchronization and Timing of Epileptiform Bursts in Hippocampal CA3 Pyramidal Neurons

Journal of Neurophysiology ◽

10.1152/jn.00434.2006 ◽

2006 ◽

Vol 96 (6) ◽

pp. 3028-3041 ◽

Cited By ~ 32

Author(s):

David Fernández de Sevilla ◽

Julieta Garduño ◽

Emilio Galván ◽

Washington Buño

Keyword(s):

Neuronal Excitability ◽

Pyramidal Neurons ◽

Epileptiform Activity ◽

Network Activity ◽

Cellular Mechanisms ◽

Burst Frequency ◽

Potassium Conductances ◽

Hippocampal Ca3 ◽

Ca3 Pyramidal Neurons

Calcium-activated potassium conductances regulate neuronal excitability, but their role in epileptogenesis remains elusive. We investigated in rat CA3 pyramidal neurons the contribution of the Ca2+-activated K+-mediated afterhyperpolarizations (AHPs) in the genesis and regulation of epileptiform activity induced in vitro by 4-aminopyridine (4-AP) in Mg2+-free Ringer. Recurring spike bursts terminated by prolonged AHPs were generated. Burst synchronization between CA3 pyramidal neurons in paired recordings typified this interictal-like activity. A downregulation of the medium afterhyperpolarization (mAHP) paralleled the emergence of the interictal-like activity. When the mAHP was reduced or enhanced by apamin and EBIO bursts induced by 4-AP were increased or blocked, respectively. Inhibition of the slow afterhyperpolarization (sAHP) with carbachol, t-ACPD, or isoproterenol increased bursting frequency and disrupted burst regularity and synchronization between pyramidal neuron pairs. In contrast, enhancing the sAHP by intracellular dialysis with KMeSO4 reduced burst frequency. Block of GABAA–B inhibitions did not modify the abnormal activity. We describe novel cellular mechanisms where 1) the inhibition of the mAHP plays an essential role in the genesis and regulation of the bursting activity by reducing negative feedback, 2) the sAHP sets the interburst interval by decreasing excitability, and 3) bursting was synchronized by excitatory synaptic interactions that increased in advance and during bursts and decreased throughout the subsequent sAHP. These cellular mechanisms are active in the CA3 region, where epileptiform activity is initiated, and cooperatively regulate the timing of the synchronized rhythmic interictal-like network activity.

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Short-Term Epileptiform Activity Potentiates Excitatory Synapses but Does Not Affect Intrinsic Membrane Properties of Pyramidal Neurons in the Rat Hippocampus In Vitro

Biomedicines ◽

10.3390/biomedicines9101374 ◽

2021 ◽

Vol 9 (10) ◽

pp. 1374

Author(s):

Julia L. Ergina ◽

Dmitry V. Amakhin ◽

Tatyana Y. Postnikova ◽

Elena B. Soboleva ◽

Aleksey V. Zaitsev

Keyword(s):

Pyramidal Neurons ◽

Amplitude Ratio ◽

Glutamate Release ◽

Epileptiform Activity ◽

Hippocampal Slices ◽

Epileptic Seizures ◽

Input Resistance ◽

Membrane Properties ◽

Intrinsic Membrane Properties

Even brief epileptic seizures can lead to activity-dependent structural remodeling of neural circuitry. Animal models show that the functional plasticity of synapses and changes in the intrinsic excitability of neurons can be crucial for epileptogenesis. However, the exact mechanisms underlying epileptogenesis remain unclear. We induced epileptiform activity in rat hippocampal slices for 15 min using a 4-aminopyridine (4-AP) in vitro model and observed hippocampal hyperexcitability for at least 1 hour. We tested several possible mechanisms of this hyperexcitability, including changes in intrinsic membrane properties of neurons and presynaptic and postsynaptic alterations. Neither input resistance nor other essential biophysical properties of hippocampal CA1 pyramidal neurons were affected by epileptiform activity. The glutamate release probability also remained unchanged, as the frequency of miniature EPSCs and the paired amplitude ratio of evoked responses did not change after epileptiform activity. However, we found an increase in the AMPA/NMDA ratio, suggesting alterations in the properties of postsynaptic glutamatergic receptors. Thus, the increase in excitability of hippocampal neural networks is realized through postsynaptic mechanisms. In contrast, the intrinsic membrane properties of neurons and the probability of glutamate release from presynaptic terminals are not affected in a 4-AP model.

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Short-term Epileptiform Activity Potentiates Excitatory Synapses but does not Affect Intrinsic Membrane Properties of Pyramidal Neurons in the Rat Hippocampus in Vitro

10.20944/preprints202109.0316.v1 ◽

2021 ◽

Author(s):

Julia L. Ergina ◽

Dmitry V. Amakhin ◽

Tatyana Y. Postnikova ◽

Elena B. Soboleva ◽

Aleksey V. Zaitsev

Keyword(s):

Pyramidal Neurons ◽

Amplitude Ratio ◽

Glutamate Release ◽

Epileptiform Activity ◽

Hippocampal Slices ◽

Epileptic Seizures ◽

Input Resistance ◽

Membrane Properties ◽

Intrinsic Membrane Properties

Even brief epileptic seizures can lead to activity-dependent structural remodeling of neural circuitry. Animal models show that the functional plasticity of synapses and changes in the intrinsic excitability of neurons can be crucial for epileptogenesis. However, the exact mechanisms underlying epileptogenesis remain unclear. We induced epileptiform activity in rat hippocampal slices for 15 min using a 4-aminopyridine (4-AP) in vitro model and observed hippocampal hyperexcitability for at least 1 hour. We tested several possible mechanisms of this hyperexcitability, including changes in intrinsic membrane properties of neurons, presynaptic and postsynaptic alterations. Neither input resistance nor other essential biophysical properties of hippocampal CA1 pyramidal neurons were affected by epileptiform activity. The glutamate release probability also remained unchanged, as the frequency of miniature EPSCs and the paired amplitude ratio of evoked responses did not change after epileptiform activity. However, we found an increase in the AMPA/NMDA ratio, suggesting alterations in the properties of postsynaptic glutamatergic receptors. Thus, the increase in excitability of hippocampal neural networks is realized through postsynaptic mechanisms. In contrast, the intrinsic membrane properties of neurons and the probability of glutamate release from presynaptic terminals are not affected in a 4-AP model.

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Dementia with Lewy bodies—associated ß-synuclein mutations V70M and P123H cause mutation-specific neuropathological lesions

Human Molecular Genetics ◽

10.1093/hmg/ddab036 ◽

2021 ◽

Author(s):

Maryna Psol ◽

Sofia Guerin Darvas ◽

Kristian Leite ◽

Sameehan U Mahajani ◽

Mathias Bähr ◽

...

Keyword(s):

Neuronal Network ◽

Dementia With Lewy Bodies ◽

Lewy Bodies ◽

Sporadic Case ◽

Network Activity ◽

Proteinase K ◽

Neuronal Network Activity ◽

Distinct Disease

Abstract ß-Synuclein (ß-Syn) has long been considered to be an attenuator for the neuropathological effects caused by the Parkinson’s disease-related α-Synuclein (α-Syn) protein. However, recent studies demonstrated that overabundant ß-Syn can form aggregates and induce neurodegeneration in CNS neurons in vitro and in vivo, albeit at a slower pace as compared to α-Syn. Here we demonstrate that ß-Syn mutants V70M, detected in a sporadic case of Dementia with Lewy Bodies (DLB), and P123H, detected in a familial case of DLB, robustly aggravate the neurotoxic potential of ß-Syn. Intriguingly, the two mutations trigger mutually exclusive pathways. ß-Syn V70M enhances morphological mitochondrial deterioration and degeneration of dopaminergic and non-dopaminergic neurons, but has no influence on neuronal network activity. Conversely, ß-Syn P123H silences neuronal network activity, but does not aggravate neurodegeneration. ß-Syn WT, V70M and P123H formed proteinase K (PK) resistant intracellular fibrils within neurons, albeit with less stable C-termini as compared to α-Syn. Under cell free conditions, ß-Syn V70M demonstrated a much slower pace of fibril formation as compared to WT ß-Syn, and P123H fibrils present with a unique phenotype characterized by large numbers of short, truncated fibrils. Thus, it is possible that V70M and P123H cause structural alterations in ß-Syn, that are linked to their distinct neuropathological profiles. The extent of the lesions caused by these neuropathological profiles is almost identical to that of overabundant α-Syn, and thus likely to be directly involved into etiology of DLB. Over all, this study provides insights into distinct disease mechanisms caused by mutations of ß-Syn.

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Neuromodulation of Astrocytic K+ Clearance

International Journal of Molecular Sciences ◽

10.3390/ijms22052520 ◽

2021 ◽

Vol 22 (5) ◽

pp. 2520

Author(s):

Alba Bellot-Saez ◽

Rebecca Stevenson ◽

Orsolya Kékesi ◽

Evgeniia Samokhina ◽

Yuval Ben-Abu ◽

...

Keyword(s):

Oscillatory Behavior ◽

Network Activity ◽

Oscillatory Activity ◽

Extracellular Potassium ◽

Uptake Mechanism ◽

Kir Channels ◽

Neuronal Network Activity ◽

Clearance Process ◽

Spatial Buffering ◽

The Impact

Potassium homeostasis is fundamental for brain function. Therefore, effective removal of excessive K+ from the synaptic cleft during neuronal activity is paramount. Astrocytes play a key role in K+ clearance from the extracellular milieu using various mechanisms, including uptake via Kir channels and the Na+-K+ ATPase, and spatial buffering through the astrocytic gap-junction coupled network. Recently we showed that alterations in the concentrations of extracellular potassium ([K+]o) or impairments of the astrocytic clearance mechanism affect the resonance and oscillatory behavior of both the individual and networks of neurons. These results indicate that astrocytes have the potential to modulate neuronal network activity, however, the cellular effectors that may affect the astrocytic K+ clearance process are still unknown. In this study, we have investigated the impact of neuromodulators, which are known to mediate changes in network oscillatory behavior, on the astrocytic clearance process. Our results suggest that while some neuromodulators (5-HT; NA) might affect astrocytic spatial buffering via gap-junctions, others (DA; Histamine) primarily affect the uptake mechanism via Kir channels. These results suggest that neuromodulators can affect network oscillatory activity through parallel activation of both neurons and astrocytes, establishing a synergistic mechanism to maximize the synchronous network activity.

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Effect of Common Anesthetics on Dendritic Properties in Layer 5 Neocortical Pyramidal Neurons

Journal of Neurophysiology ◽

10.1152/jn.01126.2007 ◽

2008 ◽

Vol 99 (3) ◽

pp. 1394-1407 ◽

Cited By ~ 28

Author(s):

Sarah Potez ◽

Matthew E. Larkum

Keyword(s):

High Frequency ◽

Pyramidal Neurons ◽

Animal Experiments ◽

Apical Dendrite ◽

Network Activity ◽

Calcium Spikes ◽

Firing Properties ◽

The Impact

Understanding the impact of active dendritic properties on network activity in vivo has so far been restricted to studies in anesthetized animals. However, to date no study has been made to determine the direct effect of the anesthetics themselves on dendritic properties. Here, we investigated the effects of three types of anesthetics commonly used for animal experiments (urethane, pentobarbital and ketamine/xylazine). We investigated the generation of calcium spikes, the propagation of action potentials (APs) along the apical dendrite and the somatic firing properties in the presence of anesthetics in vitro using dual somatodendritic whole cell recordings. Calcium spikes were evoked with dendritic current injection and high-frequency trains of APs at the soma. Surprisingly, we found that the direct actions of anesthetics on calcium spikes were very different. Two anesthetics (urethane and pentobarbital) suppressed dendritic calcium spikes in vitro, whereas a mixture of ketamine and xylazine enhanced them. Propagation of spikes along the dendrite was not significantly affected by any of the anesthetics but there were various changes in somatic firing properties that were highly dependent on the anesthetic. Last, we examined the effects of anesthetics on calcium spike initiation and duration in vivo using high-frequency trains of APs generated at the cell body. We found the same anesthetic-dependent direct effects in addition to an overall reduction in dendritic excitability in anesthetized rats with all three anesthetics compared with the slice preparation.

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Silencing-Induced Metaplasticity in Hippocampal Cultured Neurons

Journal of Neurophysiology ◽

10.1152/jn.90378.2008 ◽

2008 ◽

Vol 100 (2) ◽

pp. 690-697 ◽

Cited By ~ 14

Author(s):

Irina V. Sokolova ◽

Istvan Mody

Keyword(s):

Hippocampal Neurons ◽

Channel Blocker ◽

Recovery Period ◽

Long Term Potentiation ◽

Homeostatic Plasticity ◽

Membrane Properties ◽

Postsynaptic Currents ◽

Short Period ◽

Spiking Activity

Silencing-induced homeostatic plasticity is usually expressed as a change in the amplitude or the frequency of miniature postsynaptic currents. Here we report that, prolonged (∼24 h) silencing of mature (20–22 days in vitro) cultured hippocampal neurons using the voltage-gated sodium channel blocker tetrodotoxin (TTX) produced no effects on the amplitude or frequency of the miniature excitatory postsynaptic currents (mEPSCs). However, the silencing changed the intrinsic membrane properties of the neurons, resulting in an increased excitability and rate of action potentials firing upon TTX washout. Allowing neurons to recover in TTX-free recording solution for a short period of time after the silencing resulted in potentiation of mEPSC amplitudes. This form of activity-dependent potentiation is different from classical long-term potentiation, as similar potentiation was not seen in nonsilenced neurons treated with bicuculline to raise their spiking activity to the same level displayed by the silenced neurons during TTX washout. Also, the potentiation of mEPSC amplitudes after the recovery period was not affected by the N-methyl-d-aspartate receptor blocker d-2-amino-5-phosponopentanoic acid or by the calcium/calmodulin-dependent kinase II (CaMKII) inhibitor KN-62 but was abolished by the L-type calcium channel blocker nifedipine. We thus conclude that the potentiation of mEPSC amplitudes following brief recovery of spiking activity in chronically silenced neurons represents a novel form of metaplasticity that differs from the conventional models of homeostatic synaptic plasticity.

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