Meeting Abstract
The isolated earthworm pharynx displays a complex pattern of contractions with both large and small peak amplitudes which can be modified by neurotransmitters. Previously we showed that FMRFamide caused changes in both the large and small amplitude contractions. Since APKQYVRFamide is a FaRP native to genus Lumbricus we decided to determine the effects of this peptide on the pharynx. The organ was removed from the animal, placed in a tissue bath filled with 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 placed into bath and the resulting changes in contraction rate and amplitude were used to create log-concentration response curves. APKQYVRFamide caused a concentration-dependent decrease in large contraction rate with a threshold of 10-7 M. The peptide caused a complex response in amplitude with an increase at 10-10 M, a decrease in at 10-8 M, an increase at 10-7 M, and a final decrease at 10-6 M. On the small peaks it caused a biphasic effect on rate with an increase at 10-8 M and a decrease at 10-7 M. The effect on amplitude of the smaller peaks was complex. A decrease occurred at 10-8 M, an increase at 10-7 M, and a decrease at 10-6 M. These responses are different from those elicited by FMRFamide and may be due to the peptide native to Lumbricus acting on a separate receptor from that of FMRFamide or regulation of the receptor is controlled by a different set of cues, but more experiments need to be performed to verify these results. Future experiments include examining substitutions to the C-terminal tetrapeptide to determine their effect on contractile activity.
