Development and optimization of a high-throughput electrophysiology assay for neuronal α4β2 nicotinic receptors

Historically, the identification of alpha 4 beta 2 nicotinic acetylcholine receptor ligands has been based on high-throughput radioligand binding, rubidium efflux assays and Ca++ flux assays using a fluorometric imaging plate reader (FLIPR). Among other approaches, low-throughput electrophysiological assays in Xenopus oocytes and two channel application liquid filament systems for mammalian cells have been commonly used. More recent technical innovations that have been introduced into the field of electrophysiology allow for automated simultaneous multi-channel operation. Here we report the development and optimization of a high-throughput electrophysiological assay for identifying functionally active alpha 4 beta 2 nicotinic receptor ligands using such a system. Characterization of the test system yielded results comparable to those obtained by other investigators using conventional electrophysiological assays. For example, the concentration-response relationships obtained for alpha 4 beta 2 receptor activation by acetylcholine and nicotine were best described by biphasic Hill equations, and the inhibition of alpha 4 beta 2 receptor currents by the nicotinic antagonist dihydro-beta-erythroidine was consistent with previously published results. Functional up-regulation of alpha 4 beta 2 receptors by prolonged exposure to nicotine or lower temperature was also confirmed. Using this methodology we were able to characterize the activation of alpha 4 beta 2 receptors by multiple compounds in a mammalian cell expression system, exemplifying its utility for rapid identification of novel nicotinic ligands within a screening cascade. Our results demonstrate the utility of this electrophysiological tool for the discovery of alpha 4 beta 2 nicotinic acetylcholine receptor ligands with potential applications in numerous clinical indications. (C) 2009 Elsevier B.V. All rights reserved.