Meeting Abstract

P2.88  Tuesday, Jan. 5  The Intesintal FMRFamide Receptor in the Earthworm Lumbricus terrestris MILLER, T.M.*; KRAJNIAK, K.G.; Southern Il. Univ. Edwardsville; Southern Il. Univ. Edwardsville tylmill@siue.edu

The motility of the earthworm digestive tract is modulated by the neuropeptide FMRFamide. Our lab has shown that this peptide has an effect on the muscular activity of both the crop-gizzard and the intestine. FMRFamide increased the rate of contractions in both organs. The focus of this project was to determine whether the same FMRFamide receptor regulates both tissues using a series of FMRFamide analogs. The intestine was removed from the animal and placed in a tissue bath. Contractions were measured with a force transducer, and analyzed using LabScribe. Increasing concentrations of peptide were added to the tissue bath and the resulting changes in contractions were used to generate a log-dose response curve. To determine which amino acids in the FMRFamide sequence were critical for biological activity we used peptides in which one of the amino acids was changed from the normal L-conformation to the D-conformation. The resulting dose-response curves were compared to that of the standard FMRFamide. FMRFamide caused an increase in the rate of contractions of the intestine with a threshold between 0.1 to 1 nM. When the C-terminal phenylalanine was changed to the D-conformation there was no response from the intestine to concentrations as high as 10 µM. The same reponses were observed in the isolated crop-gizzard. Thus the receptor in both organs requires a C-terminal L-phenylalanine for biological activity. We are currently examining the effects of D-conformational substitutions in the other three positions.