RPCH modulation of a multi-oscillator network: effects on the pyloric network of the spiny lobster

The neuropeptide red pigment concentrating hormone (RPCH), which we have pr eviously shown to activate the cardiac sac motor pattern and lead to a conj oint gastric mill-cardiac sac pattern in the spiny lobster Panulirus, also activates and modulates the pyloric pattern. Like the activity of gastric m ill neurons in RPCH, the pattern of activity in the pyloric neurons is cons iderably more complex than that seen in control saline. This reflects the i nfluence of the cardiac sac motor pattern, and particularly the upstream in ferior ventricular (IV) neurons, on many of the pyloric neurons. RPCH inten sifies this interaction by increasing the strength of the synaptic connecti ons between the IV neurons and their targets in the stomatogastric ganglion . At the same time, RPCH enhances postinhibitory rebound in the lateral pyl oric (LP) neuron. Taken together, these factors largely explain the complex pyloric pattern recorded in RPCH in Panulirus.