FMRFamide (FMRFa) was originally isolated as a cardioacceleratory peptide from mollusks. To date, a number of biologically active FMRFas and their related peptides have been identified.
Target cells and function The predominant effect of FaRPs is the reduction of spontaneous muscle contractions, such as in the intestinal muscle and the heart rate. Among FaRP subtypes, some FaRPs function in gut contraction and other subtypes do not. Physiological discrimination according to different subtype of FaRPs results in extensive functions.For example, FaRPs exert acceleratory effects on the heart rate, inhibitory effects on gut motility, and modulate synaptic activity. Furthermore, sequential ecdysis behavior is also regulated by FaRPs, consequently activating the downstream of the eclosion hormone (EH) and ecdysistriggering hormone (ETH).During ecdysis, FaRP-expressing Tv neurons are activated by ETH.
Gene, mRNA, and precursor D. melanogaster FMRFa mRNA produces a deduced prepropeptide composed of 347 aa. The prepropeptide is composed of a signal sequence, and 10 copies of FMRFa and extended FaRPs. The mature peptides are processed proteolytically and amidated at each C-terminal of the peptides.
Phe-Met-Arg-Phe, amide dose dependently (ED50=23 nM) activates a K+ current in the peptidergic caudodorsal neurons.
Phe-Met-Arg-Phe, amide (FMRFamide) stimulates growth hormone secretion in conscious OVX rats. The presence of Phe-Met-Arg-Phe, amide-like immunoreactivity in neuronal elements in the hypothalamus suggested a role for this in the hypothalamic control of the anterior pituitary function. The injection of 200 ng (313.8 picomoles) of FMRFamide (in 2 uL) produces a significantly increased plasma GH 15 min after injection. The GH-increasing effect of 400-800 ng (627-1255 picomoles) of FMRFamide is already developed after 5 min and lasted up to 30 min[3].
[1] Kits KS, et al. Phe-Met-Arg-Phe-amide activates a novel voltage-dependent K+ current through a lipoxygenasepathway in molluscan neurones. J Gen Physiol. 1997 Nov;110(5):611-28. DOI:
10.1085/jgp.110.5.611[2] Sorenson RL, et al. Phe-met-arg-phe-amide (FMRF-NH2) inhibits insulin and somatostatin secretion and anti-FMRF-NH2 sera detects pancreatic polypeptide cells in the rat islet. Peptides. 1984 Jul-Aug;5(4):777-82. DOI:
10.1016/0196-9781(84)90021-4[3] Ottlecz A, et al. Phe-Met-Arg-Phe-amide (FMRFamide) stimulated growth hormone secretion in conscious OVX rats. Neuropeptides. 1987 Feb-Mar;9(2):161-7. DOI:
10.1016/0143-4179(87)90054-0
