This award will support collaborative research in behavioral neuroendocrinology between Dr. Allen I. Selverston, University of California at San Diego, and Dr. Dr. Allain Van Wormhoudt, Laboratory for Marine Biology, College of France, Concarnu, France. The objective of the project is to purify, sequence and synthesize a crustacean CCK-like peptide from the spiny lobster Panulirus interruptus, and to determine its physio- logical activity on the gastric mill network in the stomato- gastric ganglion. This peptide has profound modulatory effects on a simple neural circuit, the gastric mill circuit of crustaceans, and is involved in the feeding- induced activation of the gastric mill. Obtaining a sequence from this peptide will allow the investigators to study in detail the mechanisms by which a neuropeptide activates and modulates a well understood neural circuit. This project is of particular importance, since the lobster CCK-like peptide is the first peptide modulating the stomatogastric rhythms, whose patterns of release in the lobster have been shown. The stomatogastric system has been for many years one of the most important and instructive model systems available for studying both the control of rhythmic patterns and its modulation by various neurotrans- mitters. This project will take advantage of the known information to enhance our understanding of these modulatory processes. The project will benefit from the mutual expertise of the two investigators: Dr. Selverston is a leader in the field of small systems neurobiology and Dr. Von Wormhoudt is an experienced biochemist who has studied CCK in other crustacea.