Method for identifying substances that modulate the activity of cation channels activated by hyperpolarization.

Method for identifying substances that modulate the activity of hyperpolarization-activated cation channels, wherein a) cells expressing a hyperpolarization-activated cation channel are used; b) the cells are hyperpolarized in the presence of a potential-sensitive fluorescent dye using iso-osmolar buffer, free of sodium ions; c) changing the membrane potential of the cells is recorded, after the simultaneous supply of sodium ions and the substance to be studied.