Immunocytochemical localization of pedal peptide in the central nervous system of the gastropod mollusc Tritonia diomedea

Tritonia pedal ganglion peptides (TPeps) are a trio of pentadecapeptides is olated from the brain of the nudibranch Tritonia diomedea. TPeps have been shown both to increase the beating rate of ciliated cells of Tritonia and t o accelerate heart contractions in the mollusc Clione limacina. Here we exa mine the immunocytochemical distribution of TPeps in the Tritonia central n ervous system. We found the brain and buccal ganglia to be rich sources of TPep immunoreactivity. Specific cells in both structures, some of them prev iously identified, were immunoreactive. Moreover, immunoreactive fibers wer e seen connecting ganglia and exiting almost all the major nerves. In the b rain, we found that the paired, ciliated statocysts apparently receive TPep innervation. In addition, we observed unstained cell bodies in each buccal ganglion with extensive TPep immunoreactive projections surrounding their somata and primary neurites. Similar projections were not observed in the b rain. We also compared the TPep immunoreactivity with that of SCP, in the b uccal ganglia. We observed many neurons and processes that were immunoreact ive to both peptides. One neuron that contains both TPep- and SCPb-like pep tides (B12) has an identified role in the Tritonia feeding network. Togethe r, these findings suggest that TPeps may play an active role in the central nervous system of Tritonia as neurotransmitters modulating orientation, sw imming, and feeding. J. Comp. Neurol. 425:1-9, 2000. (C) 2000 Wiley-Liss, I nc.