NEURAL-NETWORK CONTROLLING FEEDING IN LYMNAEA-STAGNALIS - IMMUNOCYTOCHEMICAL LOCALIZATION OF MYOMODULIN, SMALL CARDIOACTIVE PEPTIDE, BUCCALIN, AND FMRFAMIDE-RELATED PEPTIDES

This paper investigates the distribution of four classes of neuropepti des, myomodulin, small cardioactive peptide (SCP), buccalin, and FMRFa mide, in central neurons forming the network that underlies feeding be havior in the snail Lymnaea stagnalis. Intracellular dye-marking and i mmunocytochemical analysis, using antisera to the different classes of peptides, were applied to identified neurons of all three levels of t he hierarchy of the circuitry: modulatory interneurons (cerebral giant cells, CGC; slow oscillator, SO), central pattern generator (CPG) int erneurons (Nl, N2, N3), motoneurons (B1-B10), and their peripheral tar get organs. Myomodulin immunoreactivity was detected in the CGC intern eurons, in the SO, and in ventral N2-type CPG interneurons. Several la rge buccal motoneurons, the paired B1, B2, B3, B7, and neurons located in the dorsal posterior area (putative B4 cluster types) were also my omodulin immunoreactive. Target organs of buccal motoneurons, the bucc al mass, salivary glands, and oesophagus contained myomodulin-immunopo sitive fibers. SCP appeared in N2-type interneurons and was found colo calized with myomodulin in the B1 and B2 motoneurons. SCP-containing n eurons in the B4 cluster area were also detected. The buccal mass and salivary glands exhibited SCP-immunoreactive fibers. Buccalin immunore activity was scarce in the buccal ganglia and was identified only in N 1-type interneurons and three pairs of dorsal posterior neurons. In th e periphery, immunoreactive fibers were localized in the oesophagus on ly. None of the buccal neuronal types examined revealed immunoreactivi ty to SEQPDVDDYLRDWLQSEEPLY (''SEEPLY''), a peptide encoded in the FMR Famide precursor protein of Lymnaea. SEEPLY immunoreactivity was confi ned to a pair of novel ventral neurons with projections to the laterob uccal nerve innervating the buccal mass. Immunoreactive fibers were al so traced in this organ. (C) 1994 Wiley-Liss, Inc.