Localization of neuropeptides in the nervous system of the marine annelid Sabellastarte magnifica.

Immunohistochemical studies of the nervous system of Sabellastarte magnifica, a sedentary polychaete, showed the presence of neuropeptide expressing cells and fibers within the double ventral nerve cord. Immunoreactivity to cholecystokinin, neuropeptide Y, enkephalins, substance P, and FMRFamide was found to be present in specific populations of cells, identifiable by their location and by the neuropeptide they expressed. Fibers expressing the various neuropeptides were also observed in particular locations within the nerve cord. This characteristic distribution of the various neuron subgroups and fiber pathways may represent functional circuits within the nervous system of this annelid.