<p> Previous studies have shown that FMRFamide alters the contractions of the smooth muscle tissues in <i>Lumbricus terrestris</i> including muscles along the body wall. Recently, numerous new annelid FMRFamide-related peptides (FaRPs) have been identified across the annelid in both polychates and clitellates, including tetrapeptides and N-terminally extended peptides. The primary objectives of this study are to analyze and compare the effects of FMRFamide (phenylalanine-methionine-arginine-phenylalanine-NH2), YMRFamide (tyrosine-methionine-arginine-phenylalanine-NH<sub>2</sub>), FVRFamide (phenylalanine-valine-arginine-NH<sub> 2</sub>), YVRFamide (tyrosine-valine-arginine-phenylalanine-NH<sub>2</sub>), AGAYVRFamide (alanine-glycine-alanine-tyrosine-valine-arginine-phenylalanine-NH<sub> 2</sub>), PAKHYVRFamide (proline-alanine-lysine-histidine-tyrosine-valine-arginine-phenylalanine-NH<sub> 2</sub>), and APKQYVRFamide (alanine-proline-lysine-glutamine-tyrosine-valine-arginine-phenylalanine-NH<sub> 2</sub>) on the longitudinal muscles of the body wall, specifically contraction rate and contraction strength. A body wall strip without the ventral nerve cord was placed in a tissue bath and exposed to increasing concentrations of these neuropeptides. Mechanical contractions were recorded on a computer with a Grass force transducer attatched to an Iworx A/D converter. </p><p> FMRFamide decreased contraction rate at a threshold of 10<sup>-7</sup> to 10<sup>-6</sup> M and increased the contraction amplitude at 10<sup> -7</sup> to 10<sup>-6</sup> M. YMRFamide had no effect on contraction rate, while being excitatory on contraction strength with a threshold of 10<sup> -7</sup> M. FVRFamide had no effect on contraction rate, while being excitatory on contraction strength at 10<sup>-9</sup> M. YVRFamide inhibited contraction rate with a threshold of 10<sup>-9</sup> M and increased contraction strength at 10<sup>-9</sup> M. APKQYVRFamide showed a biphasic response with regards to rate, decreasing it at 10<sup>-9</sup> M and increasing at 10<sup> -8</sup> M; it increased amplitude with a threshold at 10<sup>-9</sup> M. PAKHYVRFamide decreased rate at a threshold of 10<sup>-9</sup> M; it showed a biphasic trend in regards to contraction amplitude, increasing strength at 10<sup>-9</sup> M and decreasing it at 10<sup>-6</sup> M. AGAYVRFamide demonstrated a biphasic effect on contraction rate decreasing it at 10<sup> -9</sup> M and increasing it at 10<sup>-8</sup> M; it also showed a biphasic effect on amplitude, decreasing at 10<sup>-9</sup> M and increasing at 10<sup>-7</sup> M. The data demonstrate that both tetrapeptides and N-terminally extended peptides were biologically active in a concentration dependent manner with similar trends. This seems to suggest that there is some conservation in either neuropeptide presence or FaRP receptor across the annelid phylum. Comparing the four tetrapeptide sequences the data suggested that the second position was important for determining potency of the peptide where valine containing peptides had a lower threshold for increasing contraction rate than did the methionine containing peptides. The N-terminally extended YVRFamide data suggest that the type of extension is more crucial than the extension itself. On contraction rate AGAYVRFamide and APKQYVRFamide are both biphasic while PAKHYVRFamide is only inhibitory and is the only extended YVRFamide to have a positively charged amino acid in the X position (as in ABCX-YVRFamide), suggesting that the positive charge can negate the effect of the N-terminal extension.</p>
| Identifer | oai:union.ndltd.org:PROQUEST/oai:pqdtoai.proquest.com:10147046 |
| Date | 18 October 2016 |
| Creators | Jones, Kevin Marc |
| Publisher | Southern Illinois University at Edwardsville |
| Source Sets | ProQuest.com |
| Language | English |
| Detected Language | English |
| Type | thesis |
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