Characterization of compounds on nicotinic acetylcholine receptor alpha7 channels using higher throughput electrophysiology

Alpha7 nicotinic acetylcholine receptor channels are important ligand-gated ion channels that are fast desensitizing, cation selective and have been implicated in the pathophysiology of schizophrenia and Alzheimer's disease. We report here high quality alpha 7 parallel patch clamp recordings using the QPatch automated patch clamp system. The QPatch patch clamps up to 48 cells in parallel with the same high fidelity as conventional patch clamp. EC50 and IC50 values were comparable to values obtained with conventional patch clamp. The EC50 value for acetylcholine (ACh) on the QPatch with area under the curve (AUC) analysis was 26 mu M compared to a value of 29 mu M determined from conventional patch clamp experiments. Sequential additions of ACh can be made with minimal decay of the peak amplitude. The competitive alpha 7 antagonist methyllycaconitine (MLA) blocked currents with an IC50 value of 0.25 nM which is similar to published IC50 values for MLA. Finally, two different classes of positive allosteric modulators represented by PNU-120596 and NS-1738 elicited characteristic responses, thus allowing accurate characterization of modulation and measurements of potency. These results demonstrate that alpha 7 nicotinic acetylcholine receptor channels can be studied reliably in a higher throughput, parallel manner with the QPatch automated patch clamp system. (C) 2008 Elsevier B.V. All rights reserved.