Meeting Abstract
A wide variety of FMRFamide-related peptides (FaRPs) have been isolated from or predicted in the genomes of annelids. N-terminally extended peptides with the C-terminal sequence YVRFamide have been predicted in the classes Polychaeta and Clitellata. Prior experiments using the isolated crop-gizzard of the earthworm, Lumbricus terrestris, showed that polychaete AGAYVRFamide was excitatory, while clitellate APKQYVRFamide and PAKHYVRFamide were inhibitory on the contraction amplitude. In the same experiments we found YVRFamide, the tetrapeptide core in all three peptides, was excitatory. In this study we used AYVRFamide, QYVRFamide, and HYVRFamide on the isolated crop-gizzard to determine whether the additional amino acid on the N-terminal caused a response similar to the full peptide sequence or YVRFamide. The crop-gizzard was removed from the animal, placed in a tissue bath filled with earthworm saline, and attached to a force transducer which was connected to a computer using Iworx software to record the contractions. Increasing concentrations of peptide were injected into the tissue bath and the resulting changes in contraction rate and amplitude were used to create log-concentration response curves. Both AYVRFamide and QYVRFamide caused a decrease in amplitude with a threshold between 1 to 10 nM. HYVRFamide caused a biphasic change in amplitude with a decrease in amplitude at 1 nM and an increase in amplitude at 1 μM. Thus the addition of the next amino acid on the N-terminal of YVRFamide did not always restore the activity observed with the full peptide sequence. This suggests that the crop-gizzard receptor requires a more complete sequence than five amino acids to restore the response. In the future we will examine the effects of adding back another amino acid to the N-terminal.
