Neuropeptide-like substances in the retina of intact and tentaculectomized snails

1. Immunocytochemical investigations in normal and regenerated eyes of Helix aspersa Müller revealed a positive immunoreactivity toward antibodies directed against four biologically active peptides.

2. Eighty per cent of tentaculectomized animals regenerated all tentacular structures and the immunoreactivity was found to be identical in normal and regenerated retinas.

3. Type I photosensory cells are the only αMSH-positive structures, whereas the reactivity to the three other antibodies is localized in one (rarely two) retinal ganglion cell(s).

4. Using an elution technique, the colocalization of the three substances has been demonstrated in a unique ganglion cell.

5. These results seem to indicate that the α MSH-like substance(s) play(s) an important role in visual mechanisms, particularly in photoreception.

6. The colocalization of the three other substances in a unique ganglion cell suggests their probable crucial neuromodulatory and/or neurotransmitter function in rapid conduction of impulses to the brain.