nervous system (STNS) has proved to be a valuable related peptides (FaRPs) occurring ubiquitously in vertebrates 3221The Journal of Experimental Biology 200, 3221–3233 (1997) Printed in Great Britain © The Company of Biologists Limited 1997

projection neurons with somata located primarily in other ganglia of the stomatogastric nervous system. Our studies excited certain pyloric cells, especially the lateral pyloric (LP) and ventricular dilator (VD) neurons, and enhancedpreparation for these investigations at the cellular, circuit and behavioral levels. This system contains two well-characterized neural circuits, the pyloric and the gastric mill, which are located in the stomatogastric ganglion (STG) and which mediate rhythmic movements of the foregut. The activity of these circuits can be extensively modulated by a wide array of exogenously applied compounds, including a number of peptides (Marder, 1987; Harris-Warrick et al. 1992; Skiebe and Schneider, 1994; Blitz et al. 1995). Immunocytochemical techniques have been used to localize these peptides to cell bodies within the paired commissural ganglia (CGs) and the esophageal ganglion (OG), all of which and invertebrates. FaRPs modulate numerous processes