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

Distribution of neuropeptide F in the ventral nerve cord and its possible role on testicular development and germ cell proliferation in the giant freshwater prawn, Macrobrachium rosenbergii

Neuropeptide F in invertebrates is a homolog of neuropeptide Y in mammals and it is a member of FMRFamide-related peptides. In arthropods, such as insects, there are two types of neuropeptide F comprising long neuropeptide F (NPF) and short neuropeptide F (sNPF). Both NPFs are known to play a crucial role in the regulations of foraging, feeding-related behaviors, circadian rhythm, stress responses, aggression and reproduction in invertebrates. We have earlier found that in the giant freshwater prawn, Macrobrachium rosenbergii, there are three isoforms of NPF and four isoforms of sNPF and that NPFs are expressed in the eyestalks and brain. In the present study, we investigate further the tissue distribution of NPF-I in the ventral nerve cord (VNC) and its role in the development of testes in small male (SM) Macrobrachium rosenbergii. By immunolocalization, using the rabbit polyclonal antibody against NPF-I as a probe, we could detect NPF-I immunoreactivity in the neuropils and neuronal clusters of the subesophageal ganglia (SEG), thoracic ganglia (TG) and abdominal ganglia (AG) of the SM prawns. In functional assays, the administrations of synthetic NPF-I (KPDPTQLAAMADALKYLQELDKYYSQVSRPRFamide) and sNPF (APALRLRFamide) peptides significantly increased the growth rates of SM prawns and significantly increased the gonadosomatic index (GSI) and proliferations of early germ cells in the seminiferous tubules of their testes. It is, therefore, suggestive that NPFs may play critical roles in energy homeostasis towards promoting growth as well as testicular development in prawns that could be applied in the aquaculture of this species.

A comparative review of short and long neuropeptide F signaling in invertebrates: Any similarities to vertebrate neuropeptide Y signaling?

Neuropeptides referred to as neuropeptide F (NPF) and short neuropeptide F (sNPF) have been identified in numerous invertebrate species. Sequence information has expanded tremendously due to recent genome sequencing and EST projects. Analysis of sequences of the peptides and prepropeptides strongly suggest that NPFs and sNPFs are not closely related. However, the NPFs are likely to be ancestrally related to the vertebrate family of neuropeptide Y (NPY) peptides. Peptide diversification may have been accomplished by different mechanisms in NPFs and sNPFs; in the former by gene duplications followed by diversification and in the sNPFs by internal duplications resulting in paracopies of peptides. We discuss the distribution and functions of NPFs and their receptors in several model invertebrates. Signaling with sNPF, however, has been investigated mainly in insects, especially in Drosophila. Both in invertebrates and in mammals NPF/NPY play roles in feeding, metabolism, reproduction and stress responses. Several other NPF functions have been studied in Drosophila that may be shared with mammals. In Drosophila sNPFs are widely distributed in numerous neurons of the CNS and some gut endocrines and their functions may be truly pleiotropic. Peptide distribution and experiments suggest roles of sNPF in feeding and growth, stress responses, modulation of locomotion and olfactory inputs, hormone release, as well as learning and memory. Available data indicate that NPF and sNPF signaling systems are distinct and not likely to play redundant roles.