Immunolocalization And Effects Of Myomodulin And FMRFamide On Extracellular Potential Of Myocyte In Polyclad

Objective: Myomodulin, which is currently only discovered in invertebrates, has existed in the major groups of invertebrates. It has been proven that myomodulin plays a role as neurotransmitter, neuromodulator or neurohormone and can involve or influence a variety of important life activities such as feeding, reproduction, molting, and cardiac function.FMRFamide(Phe-Met-Arg-Phe-NH2) was originally discovered in bivalve mollusk, which plays an important role in the regulation of cardiac activity as we..ll as increases myocardial contraction force and heart rate of mollusks. It has been shown in the research of platyhelminth that FMRFamide can stimulate the pharyngeal regeneration in Dugesia japonia and have influence on the regeneration of neuron and the recovery of pharyngeal function.However, the related research of myomodulin in platyhelminthes has not been reported in detail and the related research of FMRFamide in polyclad are still lacked. In this study, the Notoplana humilis are used as experimental materials to explore the distribution and function of myomodulin and FMRFamide.Methods: Firstly, two amino acid sequences of myomodulin-like peptide are filtered in our c DNA library of Notoplana humilis, then four planaria myomodulin-like peptides are analysed and sorted in the literature by bioinformatics methods. The total six planaria myomodulin-like peptides were synthesized, myomodulin A, FMRFamide and polyclonal antibodies of certain peptides were.. purchased. Finally, the immunohistochemical localization of myomodulin A and FMRFamide were did in Notoplana humilis. The exogenous stimulation which occurred on eight types of incubation of neuropeptide peptide, was carried out on the Notoplana humilis. Meanwhile, the real-time extracellular signal of myocyte were recorded to explore the effect of neuropeptide incubation on the muscles of Notoplana humilis.The electrophysiological data were analysed in order to further explore the effects of neuropeptides.Results: In this study, the immunolocalization of myomodulin-like peptides and FMRFamide were preliminary verified in Notoplana humilis. The positive reaction of Notoplana humilis myomodulin-like peptide and FMRFamide are located in cerebral ganglion, major nerve cord, muscle nerve plexus, pharynx and genital pore.All the eight peptides have different extents of influence on the amplitude of slow wave of extracellular current. The primary influence is increasing the amplitude of slow wave peak, such as a low concentration of myomodulin A(PMSMLRLamide) can cause a significant change of the amplitude of slow wave of extracellular current(P<0.01,n=3), it can be be increased from 3.94±0.28 m V to 13.06±1.44 m V. ML001(AMRLMRLamide)is the only peptide that increases the frequency of slow wave peak of extracellular current, it can be be increased from 3.22±0.19/min to 8.88±0.33/min.Conclusion: The amino acid sequences and effect in slow wave of myomodulin-like pepties in Notoplana humilis and myomodulin A are homologous. Considering the distribution of myomodulin-like pepties in Notoplana humilis, this peptide should be a new member of myomodulin neuropeptide family.The myomodulin-like peptides and FMRFamide in this study have different extents of influence in the slow wave of extracellular current.Various of myomodulin have different influences on extracellular current. It may imply that the transduction mechanism and receptor are different in various of myomodulin.