MAJOR SPECIES VARIATION IN THE EXPRESSION OF GALANIN MESSENGER-RIBONUCLEIC-ACID IN MAMMALIAN CELIAC GANGLION

To determine whether galanin may be a sympathetic neurotransmitter in the pancreas of primates and rats as well as dogs, the expression of t he galanin gene was examined in the celiac ganglion of these species b y in situ hybridization and RIA. Intense hybridization signal for gala nin messenger RNA (mRNA) was observed in every neuronal cell body of t he dog celiac ganglion. However, significant hybridization signal for galanin mRNA was seen in only 24 +/- 5% of celiac ganglion cell bodies in monkeys and was absent in rats. RIA of celiac ganglion extracts co nfirmed this species variation; galanin-like immunoreactivity was high est in dog celiac ganglion (158 +/- 13 pmol/g), present in monkeys (34 +/- 7 pmol/g), and undetectable in rats (<0.8 pmol/g). In contrast, t he celiac ganglia of all three species showed intense hybridization si gnal for neuropeptide-Y (NPY) mRNA in the majority of neuronal cell bo dies (dog, 82 +/- 4%; monkey, 99 +/- 2%; rat, 91 +/- 3%), and the celi ac ganglion NPY immunoreactivity content was high in all three species (dog, 1064 +/- 155 pmol/g; monkey, 3180 +/- 745 pmol/g; rat, 3412 +/- 347 pmol/g). Thus, there is a marked species variation in the express ion of the galanin, but not the NPY, gene in the celiac ganglion of do gs, monkeys, and rats. These data suggest that galanin is an important sympathetic neurotransmitter in the pancreatic islets of dogs, but no t those of primates or rats.