The chimaeric peptide galantide is a high-affinity ligand for galanin receptors in membranes from rat hypothalamus, hippocampus, and spinal cord. There it reversibly blocks the neuronal actions of galanin in a dose-dependent manner. The peptide also reverses the galanin-mediated inhibition of insulin release from mouse pancreatic islets. Antagonists such as galantide are therefore of potential importance both as therapeutic agents and in studies on the physiological roles of galanin.