A qualitative approach of the Nereis neuropeptides by use of antibodies to several vertebrate peptides.

Comparison of the localization of immunoreactivities which were obtained with antibodies to ?-endorphin, ?-neoendorphin, Leu- and met-enk and dynorphin with those obtained earlier using antisera to ?-endorphin, somatostatin, CRF, GRF, ?-MSH, CCK/gastrin, VIP and substance P (Dhainaut-Courtois et al., 1985a,b) show the particular status of opiate-like substances in Nereis. Indeed, immunoreactivities for vertebrate opiates were observed quite exclusively in the brain, on paraffin embedded as well as on frozen tissue sections. Furthermore, immunoreactive neurones for dynorphin occur only in light green cells (C II cells) located in nuclei 20; axons may be followed to the infracerebral region (ICR), a neurohemal area where immunoreactive nerve fibres for Leu-enk and met-enk are also present. The question to be answered now is whether the compounds immunologically related to vertebrate opiates are authentic Nereis neurohormones released in the blood vessel or the coelom or if they act only as neuromodulators at the ICR level by controlling the activity of classical neurosecretory cells or infracerebral cells. At present, a coexistence in a single neurone of an uncharacterized Nereis neurohórmone and an opiate-like substance may also be postulated. In this study, colocalization of materials immunologically related to CCK/gastrin and GRF or CCK/gastrin and 5-HT were also demonstrated. In addition to this, the use of antibody to 5-HT allowed us to confirm previous results which were obtained with radioautography and histofluorescence methods (Dhainaut-Courtois et al. 1979a,b) and to specify the distribution of this biogenic amine in the whole CNS and in the peripheral nervous system.