The chimeric peptide M35 [galanin (1-13)-bradykinin(2-9) amide] is a high-affinity galanin receptor ligand acting as a galanin receptor antagonist in the rat spinal cord, rat hippocampus and isolated mouse pancreatic islets. The radiolabelled M35 and performed equilibrium binding studies with [125I] M35 on the rat pancreatic beta-cell line Rin m 5F. Galanin displaces [125I] M35 with the same affinity (KD = 1 nM) as it displaces [125I] galanin. Displacement of [125I] galanin by M35 from Rin m 5F cell membranes shows the presence of two binding sites for M35 with KD-values of 0.3 +/- 0.1 nM and 0.52 +/- 0.03 µ,M, respectively.