FEEDING-INDUCED CHANGES IN TEMPORAL PATTERNING OF MUSCLE-ACTIVITY IN THE LOBSTER STOMATOGASTRIC SYSTEM

In the lobster Homarus gammarus, rhythmic masticatory movements of the foregut gastric mill are generated by a small neural network in the s tomatogastric ganglion. We have used EMG recordings from intact animal s to analyse gastric network output in relation to cycle period before and after feeding. In pre-prandial conditions, muscles controlling la teral teeth closure and medial tooth protraction (driven by MG and GM motor neurons, respectively) express relatively constant, return strok e-like burst durations, but change to a variable-duration power stroke -like phenotype after feeding. In contrast, the LPG neuron-innervated lateral teeth opener muscle switches from power stroke to return strok e-like behavior. Thus alternate phases within a single motor program m ay invert their temporal properties according to the behavioral situat ion. (C) 1998 Elsevier Science Ireland Ltd. All rights reserved.