M40 (1 μM) displaces [mono[IJodo-Tyr]galanin from binding sites in the hippocampus, hypothalamus, and spinal cord. M40 has a lower affinity than galanin for all membranes. The IC50 values are 6 nM in the hippocampus, 15 nM in the hypothalamus, 12 nM in the spinal cord, and 3 nM in the insulinoma cells. M40 (1 μM) completely blocks I-labeled galanin-binding sites.