Peptide histidine-isoleucine (PHI)-immunoreactive amacrine cells in the retina of the rat

Peptide histidine-isoleucine (PHI) immunoreactivity was located in amacrine-like cells in adult rat retina by use of immunohistochemical techniques. Immunoreactive somata were found in the proximal part of the inner nuclear layer. From these somata, processes could be followed into the inner plexiform layer. The terminals of these processes were mainly found in the sublayers, 1, 2, and 3, but a few terminals were also present in the other inner plexiform sublaminae. The distribution of PHI-immunoreactive somata and processes corresponds with the cellular distribution of vasoactive intestinal peptide (VIP) and indicates a possible co-localization with this peptide.