Localization and Effects of FMRFamide Related Peptides in the Earthworm Crop-Gizzard

KLOHR, S.D.*; EDER, S.; KRAJNIAK, K.G.: Localization and Effects of FMRFamide Related Peptides in the Earthworm Crop-Gizzard

Previous studies have shown that the crop-gizzard of the earthworm, Lumbricus terrestris responds to FMRFamide. Recently, we used immunohistochemical techniques to see where FMRFamide is localized in these tissues and an isolated tissue assay to determine how they respond to FLRFamide, which is also found in annelids. FMRFamide immunoreactivity (ir-FRMFamide) was visualized by immunofluorescent staining. Tissues were removed, fixed, embedded in paraffin, sectioned, and placed onto slides. The sections were stained with rabbit antibodies to YGGFMRFamide, and visualized with goat antirabbit antibodies conjugated to fluorescene. As a control some slides were stained with preimmune rabbit serum. Slides were viewed and photographed with a fluorescent microscope. For the bioassay the crop-gizzard was removed, connected to a force transducer, and placed in a tissue bath. Mechanical recordings of the contractions were made before, during, and after the application of increasing concentrations of either FLRFamide or FMRFamide. ir-FRMFamide was found in fibers and varicosities innevating the smooth muscle of both the crop and gizzard. FLRFamide caused a biphasic response in contraction rate and amplitude. At 10 uM FLRFamide caused an increase in both parameters, while at 100 uM it caused a decrease in both parameters. The change in rate was similar to that seen with FMRFamide, however FMRFamide only caused a decrease in amplitude with a threshold between 1 and 10 nM. These results strengthen the hypothesis that FMRFamide related peptides may be used to control the movements of the crop gizzard. Furthermore, it appears there are differences in how the receptor responds to the tetrapeptides.

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