The present invention relates to a nucleic acid, preferably a DNA, comprising at least a part of the sequence of an Ih ion channel. Said sequence may e.g. be derived from a human DNA, a rat DNA, a bovine DNA, a Drosophila melanogaster DNA or a sea urchin DNA. Furthermore, the present invention relates to an mRNA molecule which contains the corresponding sequences. The invention further relates to a polypeptide or protein encoded by the nucleic acid.