Gastrin- and cholecystokinin-like immunoreactivities in the nervous systemof the earthworm

The distribution of cholecystokinin and gastrin-like immunoreactive cell bo dies and fibers in the nervous system of 2 annelid worms, Lumbricus terrest ris and Eisenia fetida, has been studied by means of immunohistochemistry. The cerebral ganglion contains 170-250, the subesophageal ganglion contains 120-150, and the ventral ganglia contain 50-75 cholecystokinin immunoreact ive cells, that represent 8-12%, 8-10% and 4-5% of the total cell number, r espectively. The anti-gastrin serum stained 330-360 nerve cells in the cere bral, 32-45 in the subesophageal and 7-25 in the ventral cord ganglia, repr esenting 15-16%, 2-3% and 0.5-2% of the total cell number. Immunopositivity was found with both antisera in the enteric nervous system, where the stom atogastric ganglia and the enteric plexus contain immunoreactive cells and fibers. Immunopositive cells were found in the epithelial and subepithelial cells, as well as in nerve cells innervating the muscular layer of the gas trointestinal tube. Various epidermal sensory cells also displayed strong i mmunoreactivity. According to our findings and the results of several funct ional studies, it is suggested that in annelids cholecystokinin- and gastri n-like peptides may be involved in digestive regulation, sensory processes and central integrating processes. (C) 1999 Elsevier Science Inc. All right s reserved.