Relaxing Action of Trp-Nle-Arg-Phe-NH2 on the Anterior Byssus Retractor Muscle of Mytilus
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In the anterior byssus retractor muscle (ABRM) of Mytilus, low concentrations of the molluscan neuropeptide Phe-Met-Arg-Phe-NH2 (FMRFamide) relax ACh-induced catch tension, whereas high concentrations cause contraction. In the present studies the actions of a FMRFamide-analog Trp-Nle-Arg-Phe-NH2 (W-Nle-RFamide) on the ABRM were investigated in order to compare them with those of FMRFamide.
The actions of W-Nle-RFamide were qualitatively similar to those of FMRFamide, but catch-relaxing activity of the former peptide was found to be 10-30 times more potent than that of the latter.
Cytochemical studies showed that FMRFamide-like immunoreactivity was localized to nerve branches in the ABRM and also to neurons in the pedal ganglion.
A peptide which structurally resembles FMRFamide may be involved in the mechanism of the control of relaxation of catch tension in the ABRM of Mytilus.
Hiroshima Journal of Medical Sciences
Hiroshima University School of Medicine