To obtain a useful mouse homolog ligand for human being-derived ligand (WO 99/48920) specific to galanin receptor.

This mouse homolog ligand comprises a peptide, its precursor, its amide, its ester or its salt which contains the amino acid sequence homologous or substantially homologous to a mouse-derived specific amino acid sequence and the amino acid sequence homologous or substantially homologous to either of three kinds of rat-derived specific amino acid sequences and exhibits an ability of combining with a galanin receptor protein. The DNA or the like encoding the peptide can be used for (i) the development of a receptor-bound assay system using a recombinant receptor protein expression system and the screening of a compound being considered for medicine or (ii) the development or the like of a medicine, e.g. a mneme ameliorative agent, an aperitive or a function regulator on uterus, ren, prostate, testis or skeletal muscle, having slight adverse drug reactions.