Localization of leech excitatory peptide, a member of the GGNG peptides, in the central nervous system of a leech (Whitmania pigra) by immunohistochemistry and in situ hybridization

We have recently isolated a myoactive peptide, called leech excitatory pept ide, belonging to the GGNG peptide family from two species of leeches, Hiru do nipponia and Whitmania pigra. Immunohistochemistry and in situ hybridiza tion were employed to localize leech excitatory peptide-like peptide(s) and its gene expression in the central nervous system of W: pigra. A pair of n euronal somata were stained by both immunohistochemistry and in situ hybrid ization in the supraesophageal, subesophageal, and segmental ganglia. In ad dition, several other neurons showed positive signals by either immunohisto chemistry or in situ hybridization in these ganglia. An immunoreactive fibe r was observed to run in the anterior root of segmental ganglion 6, which i s known to send axons to the sexual organs, though we failed to detect immu noreactivity in possible target tissues. Antiserum specificity was establis hed by enzyme-linked immunosorbent assay using different leech excitatory p eptide-related peptides. Leech excitatory peptide elicited muscular contrac tion of isolated preparations of penis and intestine at concentrations of 1 0(-8) M. These results suggest that leech excitatory peptide is a neuropept ide modulating neuromuscular transmission in multiple systems, including re gulation of reproductive behavior.