Recording of GABAA receptor-mediated Cl- currents using the IonFluxTM platform
GABA (ɣ-amino buytyric acid) is the primary inhibitory neurotransmitter in the central nervous system. GABAA receptors belong to a family of ligand gated ion channels mediating fast synaptic transmission. They are of major importance as pharmacological targets for anxiolytics (e.g. benzodiazepines), schizophrenia, and sleep aids. At least nineteen different individual GABAA receptor subunits assemble into pentameric structures in different combinations to form the native receptor ( α1-6, β1-3, ɣ1-3, δ, ρ1-3, plus minor subunits)1. When activated, these receptor/channels conduct a Cl- current that desensitizes at higher GABA concentrations, with a characteristic rate for different subunit combinations. Receptors containing α1-5 subunits, any β subunits, and the ɣ2 subunit are the most prevalent in the brain. These receptors are sensitive to benzodiazepine modulation. The search for subtype-selective drugs for GABAA channels has been hampered by the lack of suitable high throughput electrophysiology platforms with the ability to interrogate ligand gated channels.
In this report, we present assay and pharmacology data for GABA modulators of a specific GABAA receptor (α1/β3/ɣ2) expressed in HEK 293 cells using the IonFlux electrophysiology platform. The IonFlux platform is a desktop instrument (Fig. 1) that utilizes microfluidic compound delivery on timescales below 100ms, facilitating the recording of fast activating ligand gated ion channels. A large number of cells (20 per ensemble) under voltage clamp can be exposed to a compound within a short time scale in parallel across the plate. Continuous recording, coupled with fast solution exchange, enables high throughput screening against ligand-gated ion channel targets.