NEUROPEPTIDE Y-CONTAINING NERVES IN THE MAMMALIAN LIVER AND LIVER-DISEASE

The distribution pattern of NPY-immunoreactive nerve fibers in the dog , pig and human liver was immunohistochemically studied. In all specie s, NPY-immunoreactive nerve fibers were mainly distributed around the walls of the interlobular vein, interlobular hepatic artery and hepati c bile duct in the region of portal triad. In the dog, a dense network of NPY nerve fibers was also detected in the walls of portal vein and hepatic artery, where it was contacted to the smooth muscle cells. Wi thin the hepatic parenchyma, on the other hand, the density of NPY-imm unoreactive nerve fibers differs among these three species. It should be noted that the NPY-immunoreactive fibers are quite rare in the pig. The normal liver of dog and human had numerous varicose never fibers entering the hepatic parenchyma where the fibers formed a dense networ k around the liver cells. In higher magnification nerve fibers was obs erved to be localized in the surface of the hepatic cells. In the intr alobular fibrous septa of human cirrhotic liver, the density of NPY-im munoreactive nerve fibers was slightly higher than in that of normal l iver, whereas it was remarkably low inside the pseudolobules.