An Electrophysiology Assay for the Fast Characterization of GABAA Ion Channel Modulators.

Qin Chen, Juliette Johnson, Ian Spencer, Cristian Ionescu-Zanetti
Fluxion Biosciences, South San Francisco, CA


The GABAA receptors belong to a family of ligand-gated ion channels mediating fast synaptic transmission. They are drawing great attention in the pharmaceutical industry due to their potential role in the development of new therapeutics affecting anxiety, sleep disorders, and muscle relaxation. However, ligand-gated ion channel screening has been hampered by the lack of suitable high throughput electrophysiology platforms. 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 ion channels.
Here we present the use of a novel electrophysiology screening plat- form integrating a microfluidics network for the study of GABAA receptor pharmacology. This platform features fast (<100ms) solution exchange coupled with simultaneous data recording. A novel assay could monitor GABA response in real time, and obtain a 3 point EC50 dose curve within 1 minute.
The GABAA α1/β3/γ2 expressing HEK cells from Millipore were used for this study. The channel was targeted with agonists, including GABA and muscimol, inhibitors (picrotoxin, bicuculline, and gaba- zine), and positive modulators, including diazepam, zolpidem and chlordiazepoxide. The positive modulators produced concentration dependent augmentation of the GABA EC20 response. The pharmacology data determined using this method was consistent with the literature values obtained using other platforms. Statistical data for inter and intra-plate reproducibility, current stability, and Z’-values, is used to validate this approach.