The Contribution of Raised Intraneuronal Chloride to Epileptic Network Activity

Alfonsa, Hannah; Merricks, Edward M.; Codadu, Neela K.; Cunningham, Mark O.; Deisseroth, Karl; Racca, Claudia; Trevelyan, Andrew J.

doi:10.1523/jneurosci.4105-14.2015

Cited by 116 publications

(142 citation statements)

References 55 publications

(36 reference statements)

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“…4) than of previous measures of the correction of optogenetically altered chloride levels ( τ =8–12 s)2829. In cells bathed additionally in bumetanide (10 μM to block NKCC1), the recovery was significantly slower ( τ =58.2±11.5 s; n =7; P <0.025; Fig.…”

Section: Resultsmentioning

confidence: 66%

“…We tested, using multiunit recordings, whether Cl-out activation changed the entrainment of spiking to the dominant field oscillation, in the opposite direction to the effect shown previously, when we drove chloride into neurons using Halorhodopsin29. We first applied VU0463271, to load chloride generally into neurons, and then assessed spike entrainment before and after Cl-out activation.…”

Section: Resultsmentioning

confidence: 99%

“…We then delivered a series of 25 s illuminations, at 30 s intervals (83% duty cycle), using both blue (488 nm) and green light (561 nm) to activate the expressed Cl-out1 co-opsin. We tested network excitability in each cycle of illumination, during the 5 s dark period, following the same protocol described previously29. In all cases, this rapidly reversed the hyperexcitable state back to baseline levels, as measured both by the near abolition of spontaneous events (Fig.…”

Section: Resultsmentioning

confidence: 99%

“…Optogenetics has introduced many new tools for regulating neuronal function27, including the ability to load chloride into neurons using the optogenetic chloride pump, Halorhodopsin28. We used this strategy to demonstrate how raised intraneuronal chloride leads to an acute increase in network excitability29 and alterations in spike-timing, consistent with patterns of activity that have been recorded in epileptic animals3031. Similarly, the specific KCC2 antagonist, VU0463271, also rapidly induces epileptiform discharges in brain slice preparations32.…”

mentioning

confidence: 91%

“…Similarly, the specific KCC2 antagonist, VU0463271, also rapidly induces epileptiform discharges in brain slice preparations32. The influence of chloride balance on spike-timing, mediated through its effect on GABA A inhibition29, also has implications for a wide range of neuronal activity, including spike-time dependent plasticity, neuronal clustering and information transfer through networks with weak glutamatergic synaptic connections.…”

mentioning

confidence: 99%

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Cl-out is a novel cooperative optogenetic tool for extruding chloride from neurons

Alfonsa

Lakey²,

Lightowlers³

et al. 2016

Nat Commun

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Chloride regulation affects brain function in many ways, for instance, by dictating the GABAergic reversal potential, and thereby influencing neuronal excitability and spike timing. Consistent with this, there is increasing evidence implicating chloride in a range of neurological conditions. Investigations about these conditions, though, are made difficult by the limited range of tools available to manipulate chloride levels. In particular, there has been no way to actively remove chloride from neurons; we now describe an optogenetic strategy, ‘Cl-out', to do exactly this. Cl-out achieves its effect by the cooperative action of two different component opsins: the proton pump, Archaerhodopsin and a chloride channel opsin. The removal of chloride happens when both are activated together, using Archaerhodopsin as an optical voltage clamp to provide the driving force for chloride removal through the concurrently opened, chloride channels. We further show that this novel optogenetic strategy can reverse an in vitro epileptogenic phenotype.

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Section: Resultsmentioning

confidence: 66%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

mentioning

confidence: 91%

mentioning

confidence: 99%

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Cl-out is a novel cooperative optogenetic tool for extruding chloride from neurons

Alfonsa

Lakey²,

Lightowlers³

et al. 2016

Nat Commun

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Diazepam effect during early neonatal development correlates with neuronal Cl⁻

Glykys

Staley

2015

Ann Clin Transl Neurol

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ObjectiveAlthough benzodiazepines and other GABAA receptors allosteric modulators are used to treat neonatal seizures, their efficacy may derive from actions on subcortical structures. Side effects of benzodiazepines in nonseizing human neonates include myoclonus, seizures, and abnormal movements. Excitatory actions of GABA may underlie both side effects and reduced anticonvulsant activity of benzodiazepines. Neocortical organotypic slice cultures were used to study: (1) spontaneous cortical epileptiform activity during early development; (2) developmental changes in [Cl−]i and (3) whether diazepam's anticonvulsant effect correlated with neuronal [Cl−]i.MethodsEpileptiform activity in neocortical organotypic slice cultures was measured by field potential recordings. Cl− changes during development were assessed by multiphoton imaging of neurons transgenically expressing a Cl‐sensitive fluorophore. Clinically relevant concentrations of diazepam were used to test the anticonvulsant effectiveness at ages corresponding to premature neonates through early infancy.Results(1) Neocortical organotypic slices at days in vitro 5 (DIV5) exhibited spontaneous epileptiform activity. (2) Epileptiform event duration decreased with age. (3) There was a progressive decrease in [Cl−]i over the same age range. (4) Diazepam was ineffective in decreasing epileptiform activity at DIV5‐6, but progressively more effective at older ages through DIV15. (5) At DIV5‐6, diazepam worsened epileptiform activity in 50% of the slices.InterpretationThe neocortical organotypic slice is a useful model to study spontaneous epileptiform activity. Decreasing [Cl−]i during development correlates with decreasing duration of spontaneous epileptiform activity and increasing anticonvulsant efficacy of diazepam. We provide a potential explanation for the reports of seizures and myoclonus induction by benzodiazepines in newborn human neonates and the limited electrographic efficacy of benzodiazepines for the treatment of neonatal seizures.

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Hippocampal sharp wave‐ripple: A cognitive biomarker for episodic memory and planning

2015

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Sharp wave ripples (SPW-Rs) represent the most synchronous population pattern in the mammalian brain. Their excitatory output affects a wide area of the cortex and several subcortical nuclei. SPW-Rs occur during ‘off-line’ states of the brain, associated with consummatory behaviors and non-REM sleep, and are influenced by numerous neurotransmitters and neuromodulators. They arise from the excitatory recurrent system of the CA3 region and the SPW-induced excitation brings about a fast network oscillation (ripple) in CA1. The spike content of SPW-Rs is temporally and spatially coordinated by a consortium of interneurons to replay fragments of waking neuronal sequences in a compressed format. SPW-Rs assist in transferring this compressed hippocampal representation to distributed circuits to support memory consolidation; selective disruption of SPW-Rs interferes with memory. Recently acquired and pre-existing information are combined during SPW-R replay to influence decisions, plan actions and, potentially, allow for creative thoughts. In addition to the widely studied contribution to memory, SPW-Rs may also affect endocrine function via activation of hypothalamic circuits. Alteration of the physiological mechanisms supporting SPW-Rs leads to their pathological conversion, “p-ripples”, which are a marker of epileptogenic tissue and can be observed in rodent models of schizophrenia and Alzheimer’s Disease. Mechanisms for SPW-R genesis and function are discussed in this review.

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The Contribution of Raised Intraneuronal Chloride to Epileptic Network Activity

Abstract: Altered inhibitory function is an important facet of epileptic pathology. A key concept is that

Cited by 116 publications

References 55 publications

Cl-out is a novel cooperative optogenetic tool for extruding chloride from neurons

Cl-out is a novel cooperative optogenetic tool for extruding chloride from neurons

Diazepam effect during early neonatal development correlates with neuronal Cl⁻

Hippocampal sharp wave‐ripple: A cognitive biomarker for episodic memory and planning

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The Contribution of Raised Intraneuronal Chloride to Epileptic Network Activity

Abstract: Altered inhibitory function is an important facet of epileptic pathology. A key concept is that

Cited by 116 publications

References 55 publications

Cl-out is a novel cooperative optogenetic tool for extruding chloride from neurons

Cl-out is a novel cooperative optogenetic tool for extruding chloride from neurons

Diazepam effect during early neonatal development correlates with neuronal Cl−

Hippocampal sharp wave‐ripple: A cognitive biomarker for episodic memory and planning

Contact Info

Product

Resources

About

Diazepam effect during early neonatal development correlates with neuronal Cl⁻