DNSP-11 antibody signal was investigated in perfusion fixated Fischer 344 rat brains by immunohistochemistry with a custom， affinity purified polyclonal antibody. The DNSP-11-antibody signal was differentially localized from the mature GDNF protein both spatially and temporally. In the mesencephalon of post-natal day 10 animals， when GDNF is maximally expressed， DNSP-11 and GDNF antibody immunoreactivities co-localize extensively but not exclusively. In adult 3-month-old animals， GDNF expression is markedly reduced while the DNSP-11 signal remains intense. DNSP-11-antibody signal was present in the 3-month-old rat brain with signal in the substantia nigra， ventral tegmental area， dentate gyrus of the hippocampus， with the strongest signal observed in the locus ceruleus where GDNF is not expressed. While amino acid sequence homologues such as NPY and Tfg do exist， binding patterns reported in the literature of do not recapitulate the immunoreactive patterns observed for the DNSP-11-antibody signal.