Meeting Abstract
The motility of the earthworm crop-gizzard is modulated by several neurotransmitters and neuropeptides. Among these molecules are FMRFamide and APKQYVRFAmide. FMRFamide has been found in worms from every annelid class and APKQYVRFamide has been predicted in the mRNA of the earthworm Lumbricus rubellis. Previously we examined the effects of these peptides on isolated crop-gizzards of the related worm, Lumbricus terrestris. In those experiments, different animals were used to examine the effects of each peptide and we found that both peptides caused decrease in contraction amplitude. However, their effects on contraction rate were highly variable. Since these animals are wild types, we decided to examine the effects of each peptide on the same tissue to determine if there were any changes in contraction rate. The crop-gizzard was removed from the animal and placed in a tissue bath filled with aerated saline. One end of the organ was connected to a stationary support and the other was tied to a force-transducer. Contractions were recorded on a computer using Iworx Labscribe software. Alternating concentrations of APKQYVRFamide and FMRFamide were injected into the tissue bath. The resulting data were used to create log-concentration responses for each neuropeptide. Both peptides caused a decrease in contraction amplitude at 10-6 and 10-5 M, but FMRFamide showed to be more effective at inhibiting muscle contraction than APKQYVRFamide. FMRFamide caused a biphasic change in contraction rate, with an increase at 10-6 M and a decrease at 10-5 M. APKQYVRFamide caused an increase in contraction rate at 10-6 and 10-5 M. FMRFamide was more potent and efficacious in causing the contraction rate increase compared to APKQYVRFamide. The results of this study show that using the same organs to test both peptides yields clearer data than when they are tested in different organs.
