Ion channel assay methods

A method of high throughput assaying ion channel activity for testing the effect of one or more candidate compounds on biological cells, the method comprising:

• expressing a selected target ion channel in said cells;
• expressing a selected counter ion channel in said cells;
• placing said cells, solvet, voltage sensitive dyes for detecting transmembrane potential changes when said counter ion channels are open said target ion channels are blocked, and at least one candidate compound in each of a plurality of wells of a multiwell plate;
• repetitively exposing said at least one cell to a plurality of electric field pulses wherein said electric fields are produced with extracellular electrodes positioned in the solvent in each of said plurality of wells so as to cause current flow in opposite directions through cell membranes if said target ion channels are open and said counter ion channels are open;
• and
• detecting open counter ion channels and blocked target ion channels by monitoring the transmembrane potential of said cells, wherein said detecting comprises monitoring, without using a patch clamp, changes in the transmembrane potential of cells in each of said plurality of wells by monitoring emission from said voltage sensitive dyes when said target ion channels are blocked and said counter ion channels are open to test the effect of said one or more candidate compounds on said cells in a parallel assay high throughput manner.