Immunocytochemical localization of neuropeptide F-immunoreactivity in the circumoesophageal ganglia of the gastropod mollusc, Helix aspersa using electron microscopy.

Neuropeptide F (NPF)-immunoreactivity has been localized by electron microscopy in the central nervous system of the gastropod mollusc, Helix aspersa using a region-specific antiserum in conjunction with post-embedding immunogold labelling. The specific antiserum employed, designated NPF3, was raised to a synthetic N-terminal fragment of H. aspersa NPF. Gold-labelling revealed that NPF-immunoreactivity was found almost exclusively over the contents of dense-cored secretory vesicles within nerve axons in both cerebral and subesophageal ganglia. Double-labelling of NPF and FMRFamide demonstrated no apparent co-localization in the paired cerebral ganglia. Instead, immunoreactivities of the two neuropeptides were found to have distinct locations within the ganglia. These findings suggest that NPF may be an important neuroregulator in H. aspersa and that in the cerebral ganglia it may be anatomically-distinct from FMRFamide and related peptides.