Immunohistochemical demonstration of galaninlike immunoreactive nerves in the human pancreas

Galanin, the newly discovered 29 amino acid-residue peptide, has been shown to suppress glucose-induced insulin secretion in experimental animals, but its presence and physiological role in the human pancreas have not been established. In this study, the occurrence and distribution of galanin immunoreactivity in the human pancreas was investigated by immunohistochemistry. In addition, the possible coexistence of galanin and vasoactive intestinal peptide immunoreactivity in neural elements of the pancreas was examined. In the human pancreas, galanin immunoreactivity was localized in numerous nerve fibers around glandular acini, ductules and blood vessels, and in a few nerve fibers within islets. Nerve cells with galanin immunoreactivity were frequently noticed. Immunostainings for galanin and for vasoactive intestinal peptide on serial adjacent sections of intrapancreatic ganglia showed the coexistence of the two immunoreactivities in a large proportion (73.3%) of nerve cells. These observations may provide a morphological basis for the possible neurotransmitter or neuromodulator role of galanin in the human pancreas.