To determine if dog galanin is a potent inhibitor of dog insulin secre
tion we determined its primary structure from its cloned cDNA, evaluat
ed its expression in celiac ganglia and determined its effect on islet
hormone secretion. The predicted amino acid sequence differs from the
other known species of galanin by three to six amino acids in the C-t
erminal half of the molecule. In situ hybridization revealed the prese
nce of dog progalanin mRNA in every neuronal cell body in the dog celi
ac ganglion. The predicted dog galanin peptide was synthesized and inf
used i.v. at 0.25, 2.5, 25 or 250 pmol/kg/min. It potently inhibited i
nsulin secretion, less potently inhibited pancreatic somatostatin rele
ase and stimulated glucagon secretion, similar to the effects of porci
ne galanin in the dog. In summary, dog galanin is expressed in the neu
ronal cell bodies that innervate the pancreas and the sequence of the
dog galanin preserves the potent insulin inhibitory part of the galani
n molecule. These data support the hypothesis that galanin is a sympat
hetic neurotransmitter in dog pancreas.