Galanin-like immunoreactive neural elements in domestic ruminant pancreas

The distribution and ontogeny of the galanin-like immunoreactive (Gal-IR) n eural structures in the pancreas of cattle, sheep and goat were investigate d immunohistochemically. The present study confirmed the previous findings on the immunolocalization of galanin both in the neural elements and endocr ine cells of cattle, and reported for the first time its exclusive localiza tion in the neural elements of sheep and goat. The frequency of Gal-IR nerv e fibers and nerve cell bodies was high in cattle and low in sheep and goat . Their first detection was at the first fetal trimester in cattle and thir d trimester in sheep and goat. In cattle, a marked increase in the frequenc y of Gal-IR nerve fibers was observed from the third trimester to early neo natal stage followed by a decrease after three months postnatal. In contras t to the non-preferential distribution pattern in sheep, the G-al-IR nerve fibers in cattle and goat pancreas were predominantly associated with the a cini, excretory ducts and blood vessels, but rarely detected in the pancrea tic islets. The Gal-IR nerve cell bodies were observed as isolated bodies i n the intra- and interlobular connective tissues and as a group within the intrapancreatic ganglia. At the vicinity of the nerve cell bodies, Gal-IR n erve fibers were observed. The present findings may suggest that: (1) galan in regulates pancreatic function as neurotransmitter/neuromodulator in rumi nants; (2) galanin plays a more important role in large than in small rumin ants; and (3) particularly in cattle, it exerts its most dramatic effect du ring perinatal development.