Localization of Neuropeptide Y-like Immunoreactivity in the Saccus Vasculosus of Cartilaginous and Bony Fishes

Abstract

Abstract The distribution of perikarya and fibers containing neuropeptide Y (NPY)-like immunoreactant was studied in the saccus vasculosus of cartilaginous and bony fishes by immunohistochemistry using streptavidin-biotin technique. NPY-positive fibers were demonstrated in most of the 20 species examined, although the density of the fibers varied among the species. In the white sturgeon, Acipenser transmontanus, NPY-positive varicose fibers formed a supraependymal plexus. On the other hand, NPY-positive perikarya could be demonstrated in the ayu, Plecoglossus altivelis, in which an NPY-positive, presumed afferent fiber fascicle was encountered. These results suggest an involvement of NPY or related substance in the saccus vasculosus function and its regulation.