IMMUNOHISTOCHEMICAL SURVEY OF NEUROTENSIN DISTRIBUTION IN THE GASTRO-ENTERO-PANCREATIC NEUROENDOCRINE SYSTEM OF SEVERAL EUROPEAN SPECIES OF AMPHIBIANS AND REPTILES

摘要

The gastro-entero-pancreatic (GEP) system of 13 species of amphibians (newts, salamanders, frogs, toads) and reptiles (turtles, lizards, snakes) has been investigated immunohistochemically for the occurrence and topographic distribution of neurotensin (NT). With the antiserum used NT immunopositive elements (endocrine cells or/and nerve fibers) were found in all anurans and reptiles studied, whereas the immunoreaction was absent throughout the GEP system of urodeles (newts and salamanders). NT irnmunolabelled endocrine cells were most abundant in the intestine of all anurans and reptiles, appreciable less in the lower stomach of frogs and only sparse in the turtle pancreas. The NT cells of the "open" variety prevailed throughout along the guts, except the frog and snake large intestines, where the ratio between the "open" and "closed" cell varieties was fairly balanced. Contrary, in the frog lower stomach the immunostained cells were of the "closed" variety. The antiserum used revealed a relative rich innervation, besides endocrine cells in the frog gastrointestinal tract. It consisted exclusively of nerve fibers and terminals showing the highest density in the lower stomach and duodenum. This study- demonstrates for the first time the presence of NT containing cells in pancreas (turtles) and of nerve fibers immunolabelled for this neuropeptide in anuran gut (frogs). It also allows a more accurate estimation of the distribution and amounts of NT immunoreactive neural or/and endocrine elements in the GEP system of various taxa of anurans and reptiles. Finally, the results represent a further contribution to the concept of the phylogenetic perenniality of neurotensin.