Automated Electrophysiology in Drug Discovery

Abstract

Ion channels play essential roles in nervous system signaling, electrolyte transport, and muscle contraction. As such, ion channels are important therapeutic targets, and the search for compounds that modulate ion channels is accelerating. In order to identify and optimize ion channel modulators, assays are needed that are reliable and provide sufficient throughput for all stages of the drug discovery process. Electrophysiological assays offer the most direct and accurate characterization of channel activity and, by controlling membrane potential, can provide information about drug interactions with different conformational states. However, these assays are technically challenging and notoriously low-throughput. The recent development of several automated electrophysiology platforms has greatly increased the throughput of whole cell electrophysiological recordings, allowing them to play a more central role in ion channel drug discovery. While challenges remain, this new technology will facilitate the pharmaceutical development of ion channel modulators.

Role of hERG potassium channel assays in drug development

“…In both cell lines, IC 50 values were significantly right-shifted compared to those determined by electrophysiology, regardless of whether DiBAC 4 (3) (Invitrogen, Carlsbad, CA), FMP or Blue Several higher throughput automated electrophysiological instruments have been developed and typically use a planar substrate with holes, illustrated in Figure 5, that replaces the traditional patch pipette. 21,22 Cells that seal to the substrate around a hole may be voltage clamped, if the section of plasma membrane covering the hole can be ruptured manually, by applying negative pressure, or perforated using an antibiotic such as amphotericin, allowing electrical access to the cell's cytoplasm. Currently, the highest throughput devices available are the IonWorks HT and IonWorks Quattro.…”

Validation of a High-Throughput, Automated Electrophysiology Platform for the Screening of Nicotinic Agonists and Antagonists

“…2 The recent introduction of medium-and high-throughput electrophysiology platforms has allowed for the ability to assess the functional activity of a large number of compounds designed to target LGICs. Several automated electrophysiology platforms have now become commercially available for use in higher-throughput drug screening, [3][4][5] with only a handful of publications demonstrating their use for NNR compounds. [6][7][8] These studies have yielded EC 50 data from automated platforms for both α4β2 and α7 nicotinic receptors using the endogenous nicotinic ligand acetylcholine (ACh) that are highly comparable to those obtained with manual patch clamp recordings; however, these platforms cannot truly be considered high throughput.…”

A Short Guide to Electrophysiology and Ion Channels

“…The cells are placed in a single hole on the planar chip and the system generates some 100 megaohm seal. An electrical access is then attained by applying permeabilizing agent in the intracellular solution to perform a perforated patch clamp (21,22).…”

“…The TRPC4 and TRPC5 channels assemble as homomers or heteromerise with TRPC1 to allow Ca 2+ and Na + entry into cells. These homomeric or heteromeric channels can be activated by the natural product (-)-Englerin A, the metal ion Gadolinium (III) or the physiological agonist sphingosine-1-phosphate (21). The homomeric TRPC4 and TRPC5 channels can be inhibited by ML204 and by the anti-histamine Clemizole hydrochloride (98,99).…”