Assessing functional properties of ligand-gated ion channels with automated whole-cell patch clamp technology
Most ligand-gated ion channels (LGICs) are characterized by fast transient currents in response to application of agonists. Typically the time constants for activation and subsequent desensitization amount to1-100 and 10-1000 ms, respectively. Consequently, recording of proper whole-cell LGIC currents with the patch clamp technique requires a fast solution exchange system. Furthermore, characterization of LGIC blockers and modulators generally requires complex compound application protocols, because the effect of a test compound needs to be evaluated simultaneously with a tran- sient application of the agonist. These requirements challenge a realistic electrophysiological characterization of LGICs. We employed the automated QPatch 16 patch-clamp system, to characterize the effects of agonists, antagonists and activators on two types of fast LGICs: (1) GABAA (γ- amino-butyric acid A) receptors and (2) ASIC (acid sensing ion channels) types 1a and 3.