• GABAA a1b2g2

    Concentration dependent activation and desensitization of GABAA (α1β2γ2) receptors by application of 1, 3 and 10 μM GABA as measured on the Port-a-Patch)

GABAA Receptor Alpha 1 Beta 2 Gamma 2

Family:
GABA Receptors (Cys-loop ligand-gated ion channels)

Subgroups:
The GABA receptor family has further been divided into GABAA, GABAB and GABAA-ρ (also called GABAC) receptors.

Topology:
As typical for Cys-loop receptors, generally four transmembrane spanning domains TM1-TM4 form one receptor subunit, five or four subunits form a pore, several heteromeric combinations are known.
GABAA: Oligomerization of typically five subunits, heteromeric combinations are known of α subunits (GABRA1 - GABRA6), β subunits (GABRB1 - GABRB3) and γ subunits (GABRG1 - GABRG3), as well as δ (GABRD), an ε (GABRE), a π (GABRP), and a θ (GABRQ). The most common type is (α1)2(β2)2(γ2), minimal requirement is  the inclusion of α and β subunits.
GABAB: Heterodimer (GABBR1, GABBR2)
GABAA: Oligomerization of five subunits, heteromeric combinations of three GABAA-ρ subunits are known (GABRR1, GABRR2, GABRR3)

Regulation and Function:
GABAA and GABAA-ρ receptors are ligand-gated ion channels (ionotropic receptors); whereas GABAB receptors are G protein-coupled receptors (metabotropic receptors). All respond to the neurotransmitter gamma-aminobutyric acid (GABA), the main inhibitory transmitter in the mammalian CNS.

Data and Applications

GABAA Receptor (a1b2g2) - Stable Responses on Repeated Compound Addition

0GabaRepeaticon sp96   SyncroPatch 96 (a predecessor model of SyncroPatch 384PE) data and applications:

The traces show repeated application of 100 µM GABA to GABAA receptors (α1 β2 γ2) expressed in HEK 293 cells. Current amplitudes were stable over time, illustrating the reliable and fast solution excahnge supported by the SyncroPatch 96.

 

GABAA Receptor (a1b2g2) - Reliable Compound Application

p20 2 GABAicon pap   Port-a-Patch data and applications:

Ligand dependent activation of GABAA receptors can be recorded with the Laminar Flow Chamber with approx. 100 ms time constant for 10 μM GABA. Concentration dependent activation and desensitization of GABAA (α1β2γ2) receptors was obtained by applying 1, 3 and 10 μM GABA for 2.5 s at a time interval of 20 s.

GABAA Receptor (a1b2g2) - On-set of response

Gaba and close up bea

icon sp96   SyncroPatch 96 (a predecessor model of SyncroPatch 384PE) data and applications:

With the SyncroPatch 96 currents can be recorded continuously during compound application. This, in conjunction with a solution exchange time of about 100 ms, makes the SyncroPatch 96 an excellent tool for investigations of ligand gated ion channels. In the data example, 10 μM GABA was added to a HEK293 cell expressing GABAA (α1β2γ2) receptors. The boxed trace shows a close up of the GABA-response.

GABAA Receptor (a1b2g2) - Activation

application16 gabaa 1 copy

icon pl   Patchliner data and applications:

Shown is concentration dependent activation of GABAA (α1β2γ2) receptors by 1, 3 and 10 μM GABA from a GABAA (α1β2γ2) expressing HEK293 cell. The rising phase in enlarged in the lower graph.

 

 

 

Application Notes

Publications

2016 - Automated Patch Clamp Meets High-Throughput Screening: 384 Cells Recorded in Parallel on a Planar Patch Clamp Module

icon sp96  SyncroPatch 384PE publication in Journal of Lab Automation (2016)

2011 - State-of-the-art automated patch clamp devices: heat activation, action potentials, and high throughput in ion channel screening

icon pap   Port-a-Patch,   icon pl  Patchliner and   icon sp96   SyncroPatch 96 (a predecessor model of SyncroPatch 384PE) publication in Frontiers in Pharmacology (2011)

GABAA: Further Readings

GABAA receptors - Investigation of Modulators

p37 1 modulatorsicon pl   Patchliner data and applications:
Cells were kindly provided by AstraZeneca.

The top images show dose dependent block of GABAA currents by bicuculline. The IC50 was determined as 1.2 ± 0.2 μM (n=11). The lower graph shows the positive modulation of glycine activation of hGlyRα1. Here, six co-applications of 20 μM glycine and increasing concentrations of a positive modulator are shown.

GABAA Receptor - Stacked Application Technology

p36 3 timedIntervicon pl   Patchliner data and applications:

Ligand gated ion channels often display receptor desensitization. A method was developed to minimize ligand exposure times and intervals between ligand exposures. The pipette first aspirates buffer, then compound. When expelling this stack, the cell is first exposed to ligand and then buffer. Exposure times as low as 400 ms are possible with this method. A GABA dose response curve, aquired in this manner, is shown on the left.

GABAA Receptor - Modulator Diazepam

Diazepam

 icon sp96   SyncroPatch 96 (a predecessor model of SyncroPatch 384PE) data and applications:

Shown is a raw current response of a HEK293 cell expressing GABAA receptors to initial exposure to GABA, followed by joint exposure to GABA and diazepam (as indicated). Solutions were  stacked (layered) in the pipette to achieve brief exposure times.

GABAA Receptor - Dose Response Curves

0SyncroGabaCRC

icon sp96   SyncroPatch 96 (a predecessor model of SyncroPatch 384PE) data and applications:

Increasing concentrations of GABA were applied to each cell. Cells were from frozen stocks and were prepared for a FliPR experiment running alongside.
The corresponding online analysis of this experiment is shown in the data set "GABAA - CRC Analysis".

 

GABAA Receptor - Currents in iCell Neurons

GABA Bicuculline neurons

icon pl   Patchliner data and applications:
Cells were kindly provided by Cellular Dynamics.

Activation of GABAA receptor currents by 30 μM GABA and partial block of the current response by 1 μM bicuculline. Bicuculline was pre-applied for at least 30 s before co-application with GABA (30 μM). Approximately 50% of the current was blocked by 1 μM bicuculline.

GABAA Receptor - CRC Analysis

0GABACRC OLA

icon sp96   SyncroPatch 96 (a predecessor model of SyncroPatch 384PE) data and applications:

Online analysis results of the dose response curves were obtained with a few mouse clicks. The color code of the online analysis helps to visualize different concentrations applied.

The corresponding data traces is shown in the data set "GABAA - Dose Response Curves".

2016 - Automated Patch Clamp Meets High-Throughput Screening: 384 Cells Recorded in Parallel on a Planar Patch Clamp Module

icon sp96  SyncroPatch 384PE publication in Journal of Lab Automation (2016)

2015 - Novel screening techniques for ion channel targeting drugs

icon pl  Patchliner,   icon sp96   SyncroPatch 384PE and   Icon CE   CardioExcyte 96 publication in Channels (2015)

2014 - Crystal structure of a human GABAA receptor

icon pap  Port-a-Patch publication in Nature (2014)

2012 - Characterizing Human Ion Channels in Induced Pluripotent Stem Cell-Derived Neurons

icon pl   Patchliner publication in Journal of Biomolecular Screening (2012)

2009 - Port-a-Patch and Patchliner: High fidelity electrophysiology for secondary screening and safety pharmacology

icon pap  Port-a-Patch and   icon pl   Patchliner publication in Combinatorial Chemistry & High Throughput Screening (2009)

2007 - Automated ion channel screening: patch clamping made easy

icon pap  Port-a-Patch and   icon pl   Patchliner publication in Expert Opinion Therapeutic Targets (2007)

2006 - Microchip technology for automated and parallel patch clamp recording

icon pap  Port-a-Patch and   icon pl   Patchliner publication in Small Journal (2006)

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