A short estrogen-responsive N-terminal galanin homologue found in rat brain and gut with antiserum raised against rat galanin(1-16)

Galanin-like peptide (GALP) is currently the only known Galanin(1-29) homologue. However, three different Galanin receptors, of which GalR3 exhibits comparatively low affinity for Galanin(1-29), and molecular heterogeneity of immunoreactive Galanin are arguments for presence of other endogenous Galanin homologues. Since Antibodies recognize three-dimensional structures of 3-5 Amino acids in a peptide, we raised Antibodies in rabbits against Galanin(1-16) conjugated to bovine serum albumin, looking for the presence of endogenous N-terminal Galanin homologues in rat tissues. The antiserum selected had 7,830 times higher avidity for Galanin(1-16) compared to Galanin(1-29). A single immunoreactive component with a Stokes radius of about 8 Amino acids was found. Immunohistochemistry strongly suggested that this immunoreactivity is localised in the same neurons as Galanin(1-29). Furthermore, its concentration was increased in response to estrogen treatment in the same brain regions as Galanin(1-29), although not as rapidly. The present results indicate the presence of a novel endogenous N-terminal Galanin homologue.