THE EFFECTS OF SDRNFLRFAMIDE AND TNRNFLRFAMIDE ON THE MOTOR PATTERNS OF THE STOMATOGASTRIC GANGLION OF THE CRAB CANCER-BOREALIS

TNRNFLRFamide was isolated and sequenced from the stomatogastric nervo us system of the crab Cancer borealis by reverse-phase high performanc e liquid chromatography followed by automated Edman degradation. An SD RNFLRFamide-like peptide that exactly co-migrated with SDRNFLRFamide w as also observed. The effects of TNRNFLRFamide and SDRNFLRFamide on th e gastric and pyloric rhythms of the stomatogastric nervous system of the crab Cancer borealis were studied. Both peptides activated pyloric rhythms in quiescent preparations in a dose-dependent manner with a t hreshold between 10(-11) and 10(-10) moll-1. Both peptides increased t he pyloric rhythm frequency of preparations showing moderate activity levels and had relatively little effect on preparations that showed st rong pyloric rhythms prior to peptide application. Both peptides evoke d gastric mill activity in preparations without existing gastric rhyth ms. The activation of the gastric rhythm is associated with activation of oscillatory properties in the dorsal gastric neurone. The inductio n of gastric rhythms by these peptides was accompanied by switches fro m pyloric-timed activity to gastric-timed activity by several stomatog astric ganglion neurones. Application of these peptides provides direc t experimental control of circuit modification in the stomatogastric n ervous system.