Bicuculline, pentobarbital and diazepam modulate spontaneous GABA<sub>A</sub> channels in rat hippocampal neurons

Birnir, Bryndis; Eghbali, Mansoureh; Everitt, Andrea B.; Gage, Peter W.

doi:10.1038/sj.bjp.0703621

Cited by 28 publications

(18 citation statements)

References 28 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…t test comparisons of the slope in control versus TTX trials at each holding potential yielded ( p ϭ 0.19, 0.25, 7 ϫ 10 Ϫ10 , and 3 ϫ 10 Ϫ6 ; t test at Ϫ80, Ϫ70, Ϫ60, and Ϫ50 mV). (Bekkers et al, 1990;Bekkers and Stevens, 1995), spontaneously opening Cl Ϫ channels (Birnir et al, 2000), and various Ca 2ϩ channel subtypes (Hille, 2001), each of which can give rise to current fluctuations. Some channels may become even noisier with an internal Cs ϩ solution because the unclamped branches at the more distal parts of the membrane will depolarize, activating voltage-gated channels.…”

Section: Resultsmentioning

confidence: 99%

Intrinsic Noise in Cultured Hippocampal Neurons: Experiment and Modeling

2004

View full text Add to dashboard Cite

Ion channels open and close stochastically. The fluctuation of these channels represents an intrinsic source of noise that affects the input-output properties of the neuron. We combined whole-cell measurements with biophysical modeling to characterize the intrinsic stochastic and electrical properties of single neurons as observed at the soma. We measured current and voltage noise in 18 d postembryonic cultured neurons from the rat hippocampus, at various subthreshold and near-threshold holding potentials in the presence of synaptic blockers. The observed current noise increased with depolarization, as ion channels were activated, and its spectrum demonstrated generalized 1/f behavior. Exposure to TTX removed a significant contribution from Na ϩ channels to the noise spectrum, particularly at depolarized potentials, and the resulting spectrum was now dominated by a single Lorentzian (1/f 2 ) component. By replacing the intracellular K ϩ with Cs ϩ , we demonstrated that a major portion of the observed noise was attributable to K ϩ channels. We compared the measured power spectral densities to a 1-D cable model of channel fluctuations based on Markov kinetics. We found that a somatic compartment, in combination with a single equivalent cylinder, described the effective geometry from the viewpoint of the soma. Four distinct channel populations were distributed in the membrane and modeled as Lorentzian current noise sources. Using the NEURON simulation program, we summed up the contributions from the spatially distributed current noise sources and calculated the total voltage and current noise. Our quantitative model reproduces important voltage-and frequency-dependent features of the data, accounting for the 1/f behavior, as well as the effects of various blockers.

show abstract

Section: Resultsmentioning

confidence: 99%

Intrinsic Noise in Cultured Hippocampal Neurons: Experiment and Modeling

2004

View full text Add to dashboard Cite

show abstract

“…The channels in the outside-out patches have GABA EC 50 value of about 30 μM [15]. On the other hand, membrane patches, both on intact neurons and in ripped-off outside-out patches, that show some spontaneous channel activity from the time the patch was formed, respond without any delay to GABA applications and the channels maximal conductance is often below 40 pS [53][54][55][56][57].…”

Section: Channel Characteristicsmentioning

confidence: 98%

“…- [23,34,101] sub-maximal conductance states or variable conformations of the channel complex [52,53]. Neuronal GABA A maximal channel conductance varies from about 10 pS to about 100 pS [13,15,[52][53][54][55][56][57][58][59][60], whereas the conductance of the expressed receptors generally is lower than 40 pS [14,[61][62][63][64]. Importantly, when GABA A receptor channel-forming subunits were expressed together with the intracellular protein GABARAP in a heterologous expression system, high-conductance channels (> 40 pS) were detected with the conductance being related to the GABA concentration [14,65].…”

Section: Inhibitory Postsynaptic Proteinsmentioning

confidence: 99%

See 1 more Smart Citation

The Impact of Sub-Cellular Location and Intracellular Neuronal Proteins on Properties of GABAA Receptors

Birnir¹,

Korpi

2007

CPD

Self Cite

View full text Add to dashboard Cite

Most studies of GABA(A) receptor accessory proteins have focused on trafficking, clustering and phosphorylation state of the channel-forming subunits and as a result a number of proteins and mechanisms have been identified that can influence the GABA(A) channel expression and function in the cell plasma membrane. In the light of a growing list of intracellular and transmembrane neuronal proteins shown to affect the fate, function and pharmacology of the GABA(A) receptors in neurons, the concept of what constitutes the native GABA(A) receptor complex may need to be re-examined. It is perhaps more appropriate to consider the associated proteins or some of them to be parts of the receptor channel complex in the capacity of ancillary proteins. Here we highlight some of the effects the intracellular environment has on the GABA-activated channel function and pharmacology. The studies demonstrate the need for co-expression of accessory proteins with the GABA(A) channel-forming subunits in heterologous expression systems in order to obtain the full repertoire of GABA(A) receptors characteristics recorded in the native neuronal environment. Further studies e.g. on gene-modified animal models are needed for most of the accessory proteins to establish their significance in normal physiology and in pathophysiology of neurological and psychiatric diseases. The challenge remains to elucidate the effects that the accessory proteins and processes (e.g. phosphorylation) plus the sub-cellular location have on the "fine-tuning" of the functional and pharmacological properties of the GABA(A) receptor channels.

show abstract

“…However, only with single-channel recordings can one study the kinetic properties of the channel molecules that generate the tonic currents. Unlike synaptic channels that activate within 100 μs, the tonic GABAA channels are activated with a latency in the range of minutes from the time GABA is applied 4,7,15,16,17,18 . This delayed activation of the channels results in that many channel properties cannot be studied using whole-cell recordings.…”

Section: Discussionmentioning

confidence: 99%

GABA-activated Single-channel and Tonic Currents in Rat Brain Slices

Jin

Yang

Birnir

2011

JoVE

Self Cite

View full text Add to dashboard Cite

The GABA A channels are present in all neurons and are located both at synapses and outside of synapses where they generate phasic and tonic currents, respectively 4,5,6,7 The GABA A channel is a pentameric GABA-gated chloride channel. The channel subunits are grouped into 8 families (α1-6, β1-3, γ1-3, δ, ε, θ, π and ρ). Two alphas, two betas and one 3 rd subunit form the functional channel 8. By combining studies of sub-type specific GABA-activated single-channel molecules with studies including all populations of GABA A channels in the neuron it becomes possible to understand the basic mechanism of neuronal inhibition and how it is modulated by pharmacological agents.We use the patch-clamp technique 9,10 to study the functional properties of the GABA A channels in alive neurons in hippocampal brain slices and record the single-channel and whole-cell currents. We further examine how the channels are affected by different GABA concentrations, other drugs and intra and extracellular factors. Video LinkThe video component of this article can be found at https://www.jove.com/video/2858/ Protocol Preparation of brain slices:Experiments are done on hippocampal brain slices from postnatal 16 -22 days old Wistar rats.1. Animals are sacrificed by decapitation in accordance with local ethical guidelines and approved animal care protocols. 2. Quickly remove the brain with a spatula and cut it along the midline with a surgical blade (# 24). Place each hemisphere on a Whatman filter paper with the cut facing the paper. 3. Put a drop of superglue on the specimen disk and place the hemisphere on top of it with the cut surface facing down. Place the specimen disk in the cutting chamber of the vibratome that is filled with an ice-cold artificial cerebrospinal fluid (ACSF, please see here below 3.1). 4. Set the slice thickness to 400 μM and start cutting the brain. You will need to cut off approximately 2 mm of brain tissue before you reach the hippocampus. 5. The hippocampal slices are put into a glass petri plate filled with ACSF. The plate is placed on a black background (e.g. black paper) to allow easy visualization of the hippocampi. Isolate the hippocampus from the surrounding tissue using sharp surgical blades. Be careful not to push or pull the tissue. 6. Slices are then incubated in the ACSF solution at 37.0 °C for 1h and then stored at room temperature until experiments are done. During the one hour incubation the tissue recovers from the damage imposed by the cutting process. Preparation of pipettes for patching:1. Pipettes are made from borosilicate glass capillaries. 2. The patch-pipettes are pulled on an automated or manual pipette pullers resulting in pipettes resistance of 2 -4 MΩ for whole cell recordings or 8 -20 MΩ for single-channel recordings when filled with the appropriate pipette solution and the bath solution being the ACSF (see below, 3.1). 3. The pipettes we use for single-channel recordings are polished using a microforge where the heat from a melted glass sitting on the platinum wire makes t...

show abstract

Bicuculline, pentobarbital and diazepam modulate spontaneous GABA_A channels in rat hippocampal neurons

Cited by 28 publications

References 28 publications

Intrinsic Noise in Cultured Hippocampal Neurons: Experiment and Modeling

Intrinsic Noise in Cultured Hippocampal Neurons: Experiment and Modeling

The Impact of Sub-Cellular Location and Intracellular Neuronal Proteins on Properties of GABAA Receptors

GABA-activated Single-channel and Tonic Currents in Rat Brain Slices

Contact Info

Product

Resources

About

Bicuculline, pentobarbital and diazepam modulate spontaneous GABAA channels in rat hippocampal neurons

Cited by 28 publications

References 28 publications

Intrinsic Noise in Cultured Hippocampal Neurons: Experiment and Modeling

Intrinsic Noise in Cultured Hippocampal Neurons: Experiment and Modeling

The Impact of Sub-Cellular Location and Intracellular Neuronal Proteins on Properties of GABAA Receptors

GABA-activated Single-channel and Tonic Currents in Rat Brain Slices

Contact Info

Product

Resources

About

Bicuculline, pentobarbital and diazepam modulate spontaneous GABA_A channels in rat hippocampal neurons