The present invention relates to a nucleic acid, preferably a DNA, comprising at least a part of the sequence of an I.sub.h 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.Furthermore, the invention relates to the use of the inventive nucleic acid and proteins for a screening and/or diagnosing method and to the kits required therefor.Lastly, the invention relates to the use of one or more nucleic acids and proteins for the treatment and/or prophylaxis of cardiovascular disorders and disturbances of consciousness.