The present invention relates to recombinant seven-trans-membrane receptor, whereby the amino terminus of said recombinant receptor is located on an extracellular side and the carboxy-terminus is located on an intracellular side of a membrane, comprising at least two detectable labels, whereby a first of said at least two detectable labels is or is located on the carboxy-terminus and whereby a second of said at least two labels is or is located on the first or third intracellular loop or whereby a first of said at least two labels is or is located on the third intracellular loop. Furthermore, nucleic acid molecules encoding said recombinant seven-transmembrane receptors are described as well as vector and host cells comprising the same. Furthermore, the present invention provides for identification and screening methods for molecules or compounds which are capable of modifying the biological end of pharmacological function of seven-transmembrane receptor proteins. Finally, diagnostic compositions comprising the compounds of the present invention as well as kits comprising said compounds are disclosed.