IMMUNOCYTOCHEMICAL DISTRIBUTION OF NEUROPEPTIDE-F (NPF) IN THE GASTROPOD MOLLUSK, HELIX-ASPERSA, AND IN SEVERAL OTHER INVERTEBRATES

The distribution of neuropeptide F (NPF) immunoreactivity in the snail , Helix aspersa, has been demonstrated by immunocytochemistry using 2 region-specific antisera. One, designated NPF3, was raised against a s ynthetic N-terminal fragment of Helix aspersa NPF; the other, designat ed PP221, was raised against the C-terminal hexapeptide amide of mamma lian pancreatic polypeptide (PP) but cross-reacts fully with the analo gous C-terminal region of Helix aspersa NPF. The distribution of NPF i mmunoreactivity has also been compared with that of FMRFamide using al ternate serial sections of Helix aspersa ganglia. Results showed that NPF immunoreactivity was abundant and widespread in the central and pe ripheral nervous systems and the pattern of immunostaining obtained us ing both region-specific antisera was similar. Likewise, immunocytoche mistry of neural tissues of a congeneric species, Helix pomatia, and 2 prosobranch gastropods, Buccinum undatum and Littorina littorea, prod uced similar staining patterns with both antisera. However, in the cep halopod mollusc, Loligo vulgaris, and the cestode, Moniezia expansa, p ositive immunostaining was only obtained with the C-terminal PP antise rum. Immunostaining of alternate serial sections of Helix aspersa gang lia with NPF3, and an antiserum raised to FMRFamide, showed that while a few neurones were immunoreactive with one antiserum only, in the ma jority, both immunoreactivities were co-localised. NPF thus appears to be an important neuropeptide of widespread distribution in Helix aspe rsa and the differential immunocytochemical staining obtained using th e 2 region-specific antisera would suggest a high degree of primary st ructural conservation within the gastropod molluscs, but lack of conse rvation of the N-terminal region of the peptide in other invertebrate groups.