Pigment-dispersing hormone-like immunoreactive neurons in the central nervous system of the gastropods, Helix pomatia and Lymnaea stagnalis

By using an antiserum raised against a crustacean beta-pigment-dispersing h ormone (PDH), the distribution and chemical neuroanatomy of PDH-like immuno reactive neurons was investigated in the central nervous system of the gast ropod snails, Helix pomatia and Lymnnea stagnalis. The number of immunoreac tive cells in the Helix central nervous system was found to be large (700-9 00), whereas in Lymnaea, only a limited number (50-60) of neurons showed im munoreactivity. The immunostained neurons in Helix were characterized by ri ch arborizations in all central ganglia and revealed massive innervation of all peripheral nerves and the neural (connective tissue) sheath around the ganglia and peripheral nerve trunks. A small number of Helix nerve cell bo dies in the viscero-parietal ganglion complex were also found to be innerva ted by PDH-like immunoreactive processes. Hence, a complex central and peri pheral regulatory role, including neurohormonal actions, is suggested for a PDH-like substance in Helix, whereas the sites of action may be more limit ed in Lymnaea.