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PubMedDate not supplied

The brain of Lymnaea contains a family of FMRFamide-like peptides.

Authentic FMRFamide and two FMRFamide-related heptapeptides were purified from the central nervous system of the fresh water snail Lymnaea stagnalis. The sequences of the heptapeptides were determined as: Ser-Asp-Pro-Phe-Leu-Arg-Phe-NH2 (SDPFLRFamide) and Gly-Asp-Pro-Phe-Leu-Arg-Phe-NH2 (GDPFLRFamide) by modified Edman degradation and enzymatic digestion. Relatively high quantities of the deamidated and therefore non-immunoreactive analogs of these two peptides (SDPFLRF and GDPFLRF) were also found. SDPFLRFamide and GDPFLRFamide were synthesized and were found to be chromatographically and biologically indistinguishable from the natural peptides, confirming the sequences. The log dose-response curves for the chronotropic action of either synthetic peptide on the heart of Lymnaea was very similar to that of FMRFamide. These data indicate that Lymnaea contains a family of FMRFamide-like peptides.

Amino Acid Sequence↗
PubMedDate not supplied

FMRFamide enhances acetylcholine-induced contractions of guinea pig ileum.

Isolated guinea pig ilea were contracted with acetylcholine (ACh) in the absence and presence of the neuropeptide FMRFamide (Phe-Met-Arg-Phe-NH2). FMRFamide (0.17-17 microM) enhanced ACh-induced contractions (observed as a leftward shift of the dose-response curve and increase in Emax) with maximal effect at 1.7 microM. FMRFamide had no effect when administered alone. These results extend the demonstration of a FMRFamide/ACh interaction to mammalian tissue and support the concept that FMRFamide, or mammalian equivalents, could play a modulatory role in mammals.

Acetylcholine↗
PubMed1996

Enhanced antiopiate activity and enzyme resistance in a peptidomimetic of FMRFamide containing E-2,3-methanomethionine and E-2,3-methanophenylalanine.

FMRFamide is a molluscan peptide that has shown antiopiate activity in a number of mammalian test systems. Peptidomimetics of FMRFamide substituted with conformationally constrained stereoisomers of Z-2,3-methanomethionine or E-2,3-methanomethionine precipitated abstinence syndrome far more potently than FMRFamide itself. The current study determined the effect on antiopiate potency of an additional rigid substitution. A peptidomimetic containing a stereoisomer of E-2,3-methanomethionine was compared with a peptidomimetic additionally substituted at the C-terminal with E-2,3-methanophenylalanine. Morphine abstinence signs were observed after varying doses (0.125-25.0 micrograms) of these two peptidomimetics were injected into the third ventricle of morphine-dependent rats. The peptidomimetic containing both rigid substitutions was far more potent than the peptidomimetic of FMRFamide containing methanomethionine alone. The increased potency appears to be related to enzyme resistance rather than receptor affinity.

Amino Acid Sequence↗
PubMed1988

Dynamics of FMRFamide immunoreactivity in response to physiologically active substances in the central nervous system of the snail, Achatina fulica.

1. The changes in FMRFamide (Phe-Met-Arg-Phe-NH2) immunoreactivity in response to incubation in dopamine, serotonin, met-enkephalin, oxytocin, arg-vasopressin and FMRFamide were examined in the central nervous system of the snail, Achatina fulica. 2. When the central nervous system was cultured in medium which contained dopamine and in medium which contained serotonin, the number of immunoreactive neurons increased in the anterior part of the cerebral ganglion and decreased in the sub-esophageal ganglion. 3. When arg-vasopressin was added to the culture medium, the number of immunoreactive neurons increased in the pedal ganglion and decreased in the other sub-esophageal ganglion. 4. By contrast, when the central nervous system was cultured in medium which contained oxytocin, the number of immunoreactive neurons did not increase, but rather decreased, in each ganglion. 5. No changes in immunoreactivity were detected in the central nervous system when it was cultured in medium which contained FMRFamide. 6. It appears, from these results, that the production and release of FMRFamide from different neurons are differentially affected by the physiologically active substances tested.

Animals↗
PubMed1987

The effect of Phe-Met-Arg-Phe-NH2 (FMRFamide) on morphine-induced inhibition of colonic propulsive motility in mice.

Morphine and the molluscan neuropeptide Phe-Met-Arg-Phe-NH2 (FMRFamide) were administered to mice alone or in combination intracerebroventricularly (i.c.v.) and the effect on colonic propulsive motility was measured. Both morphine (1.0 microgram, i.c.v.) and FMRFamide (10 and 50 micrograms, i.c.v.) delayed expulsion of a 3 mm glass bead placed in the distal colon of mice compared to vehicle-treated controls. The inhibitory effects of morphine and FMRFamide on expulsion time were additive at the doses used and individually blocked by naloxone. These data suggest that FMRFamide does not antagonize this nonanalgesic effect of morphine, but appears to have opioid agonist properties.

Animals↗
PubMed1992

A lipoxygenase pathway of arachidonic acid metabolism mediates FMRFamide activation of a potassium current in an identified neuron of Helisoma.

The neuropeptide FMRFamide causes a presynaptic inhibition of neurotransmitter release from neuron B5 of Helisoma. In this study we demonstrate that one of FMRFamide's actions is to activate an outwardly rectifying potassium current. Arachidonic acid also activates an outward current in B5. The phospholipase A2 inhibitor, 4-bromophenacylbromide (BPB), and nordihydroguaiaretic acid (NDGA), an inhibitor of arachidonic acid metabolism, but not indomethacin, block FMRFamide's activation of the potassium current. Taken together these data demonstrate that one of FMRFamide's presynaptic actions is to activate a potassium current through a lipoxygenase pathway of arachidonic acid metabolism.

Acetophenones↗
PubMed1985

Cardiovascular effects of intraventricular injection of FMRFamide, Met-enkephalin and their common analogues in the rat.

The molluscan neuropeptide, Phe-Met-Arg-Phe-NH2 (FMRFamide), the mammalian opioid peptide met-enkephalin, and their common analogues, met-enkephalin-Arg6-Phe7 (YGGFMRF) and Tyr-Gly-Gly-Phe-Met-Arg-Phe-amide (YGGFMRFamide), were injected into the lateral ventricle of the rat; the cardiovascular effects were studied. FMRFamide caused a rapid, transient elevation in blood pressure accompanied by a great increase in pulse pressure. These effects were followed by secondary increases in blood and pulse pressures. Met-enkephalin produced an initial reduction in blood pressure which was followed by a gradual increase at the higher of two test doses (300 nmole). Injection of YGGFMRF resulted in a gradual increase in blood pressure. This response resembled that to met-enkephalin. The initial response to YGGFMRFamide was similar to that to FMRFamide: increases in both blood and pulse pressures after injection. However, the secondary effect of YGGFMRFamide, a prolonged reduction in blood pressure, was not produced by FMRFamide. These results suggest that the initial excitatory cardiovascular responses may be due to the presence of the C-terminal amide. All of the cardiovascular effects of injecting these peptides into the lateral ventricle were abolished by pre-treatment with naloxone in a dose that, itself, produced no cardiovascular changes. In conclusion, these peptides seem to act via the naloxone sensitive opiate receptors in the rat brain.

Animals↗
PubMed1992

The localization of FMRFamide in the nervous and somatic tissues of Nereis virens and its effects upon the isolated esophagus.

1. The tetrapeptide FMRFamide which is present in extracts of Nereis virens was localized in various nereid tissues immunohistochemically. 2. Immunoreactive FMRFamidergic cells and fibers were found in the supraesophageal (brain) and subesophageal ganglia, as well as in the intersegmental ganglia of the ventral nerve cord. Immunoreactive fibers were present in the neuropile of, and the connectives between, the supraesophageal, subesophageal, and intersegmental ganglia. 3. In the periphery immunoreactive FMRFamidergic fibers and a few cell bodies were observed in the gut. Sparse fibers were also seen in the body wall, parapodia, and cephalic palps. When the antiserum was preabsorbed with FMRFamide, no specific immunoreactivity was detected. 4. The esophagus of Nereis, isolated and suspended in a tissue bath, responded to FMRFamide with a dose-dependent relaxation; threshold was between 30 and 300 nM, and the EC50 was 1.55 +/- 0.60 microM. Benzoquinonium did not modify this response. 5. Thus, FMRFamide seems to be a neurotransmitter in both the central and peripheral nervous system of Nereis virens, and may be involved in the control of esophageal motility.

Animals↗
PubMed2006

FMRFamide-related peptides and serotonin regulate Drosophila melanogaster heart rate: mechanisms and structure requirements.

Drosophila melanogaster FMRFamide-related peptides (FaRPs) include SDNFMRFamide, PDNFMRFamide, and TDVDHVFLRFamide (dromyosuppressin, DMS); each peptide contains a C-terminal FMRFamide but a different N-terminal extension. FaRPs and serotonin (5-HT) each affect the frequency of D. melanogaster heart contractions in vivo. We examined the cellular expression of FaRPs and 5-HT, and the activities of FMRFamide, SDNFMRFamide, PDNFMRFamide, or DMS and 5-HT on heart rate. FaRPs and 5-HT were not co-localized; FaRP-and 5-HT-immunoreactive fibers extended from different brain cells and innervated the anterior D. melanogaster dorsal vessel. However, no neuron expressed both a FaRP and 5-HT. The effect of FMRFamide and 5-HT was not different from the effect of 5-HT alone on heart rate. The effect of PDNFMRFamide and 5-HT showed an additive effect on heart rate. SDNFMRFamide and 5-HT or DMS and 5-HT resulted in non-additive effects on heart rate. Our data provide evidence for the complexity of FaRP and 5-HT interactions to regulate frequency of heart contractions in vivo. Our results also confirm the biological importance of FaRP N-terminal amino acid extensions.

Amino Acid Sequence↗
PubMed2001

Location of a ligand recognition site of FMRFamide-gated Na(+) channels.

The second FMRFamide-gated Na(+) channel (HtFaNaC), from Helisoma trivolvis, has been cloned. HtFaNaC has some different pharmacological properties to HaFaNaC, from Helix aspersa, which has enabled a rational approach to be made to start to identify the FMRFamide recognition site. Several chimeras were made by switching sections between the channels. The differences in sensitivity to FMRFamide, and amiloride, were assessed after expression in Xenopus oocytes. The data suggest that a recognition site for FMRFamide, and the potentiating action of amiloride, resides in a sequence of about 120 amino acids in the extracellular loop proximal to the first transmembrane segment.

Amiloride↗
PubMed2003

The ovijector of Ascaris suum: multiple response types revealed by Caenorhabditis elegans FMRFamide-related peptides.

Caenorhabditis elegans possesses 22 FMRFamide-like peptide (flp) genes predicted to encode 60 different FMRFamide-related peptides with a range of C-terminal signatures. Peptides from five flp genes (1, 6, 8, 9 and 14) are known to modulate the ovijector of Ascaris suum in vitro. This study examines the physiological effects of peptides from the remaining 17 flp genes such that the variety of FMRFamide-related peptide-induced ovijector response types can be delineated. Five categories of response were identified according to the pattern of changes in contractile behaviour and baseline tension. Peptides encoded on 16 flp genes (1, 2, 3, 4, 6, 7, 9, 10, 11, 12, 13, 14, 15, 16, 17 and 20) had qualitatively similar inhibitory (response type 1) actions, with the lowest activity thresholds (1 nM) recorded for peptides with FIRFamide or FLRFamide C-terminal signatures. Peptides encoded on four flp genes (2, 18, 19 and 21), and on the A. suum afp-1 gene, had excitatory actions on the ovijector (response type 2), with PGVLRFamides having the lowest activity threshold (1 nM). An flp-2 peptide (LRGEPIRFamide) induced a transient contraction of the ovijector (activity threshold, 10nM) that was designated response type 3. Response type 4 comprised a transient contraction followed by an extended period of inactivity and was observed with peptides encoded on flp-5 (AGAKFIRFamide, APKPKFIRFamide), flp-8 (KNEFIRFamide) and flp-22 (SPSAKWMRFamide). SPSAKWMRFamide was the most potent peptide tested with an activity threshold of 0.1 nM. A single peptide (AMRNALVRFamide; activity threshold 0.1 microM), encoded on flp-11, induced response type 5, a shortening of the ovijector coupled with an increase in contraction frequency. Although most flp genes encode structurally related peptides that trigger one of the five ovijector response types, flp-2 and flp-11 co-encode FMRFamide-related peptides that induce distinct responses. Within the ovijector of A. suum FaRPs play a complex role involving at least five receptor subtypes or signalling pathways.

Animals↗
PubMed1997

Co-localization of serotonin and FMRFamide-like immunoreactivities in the central nervous system of the earthworm, Eisenia fetida.

In the present study co-localization of serotonin and FMRFamide-like immunoreactivities was studied in the central nervous system of the earthworm, Eisenia fetida. Alternate serial sections were stained with antisera raised against serotonin and FMRFamide, using the peroxidase-antiperoxidase method. The immunostained consecutive sections were compared by light-microscopy and on reconstructed images using NIH Image and Neurolucida programs. Although there was a large number of serotonin and FMRFamide-like immunoreactive neurons in the central nervous system of Eisenia, co-localization of immunostaining was relatively rare. In the cerebral ganglion no cells were found that stained for both antisera. In the subesophageal and ventral cord ganglia the neurons reacting for both antisera represented approximately 17-23% and 10-14% of the serotonin- and 7-11% and 9-17% of the FMRF-amide-like immunoreactive cells, respectively. It is suggested, that FMRFamide-related peptides act as neuromodulators and may also influence the activity of serotonergic neurons.

Animals↗
PubMed2001

Feeding state influences the content of FMRFamide- and tachykinin-related peptides in endocrine-like cells of the midgut of Locusta migratoria.

The midgut of 5th instar male African migratory locust, Locusta migratoria, was found to contain endocrine-like cells that stained positively for FMRFamide-like immunoreactivity. These cells have cell bodies which are tear-drop in shape with processes extending from the cell body. FMRFamide-like immunoreactivity has been described in similar cells in adult midgut tissue [16]. The midgut tissue content of FMRFamide-like immunoreactivity is differentially distributed throughout various regions of the midgut (gastric cecae, anterior and posterior midgut) in 5th instar and varied ages of adult. FMRFamide-like immunoreactivity in midgut tissues decreases significantly by 24 h of starvation, whereas locustatachykinin I-like immunoreactivity does not decrease until 48 h of starvation indicating that there are differential timing effects of these two peptide families on midgut content. HPLC analysis, combined with RIA, of different regions of the midgut tissue from both fed and starved locusts revealed that the relative proportions of the members of the two peptide families vary depending upon the feeding state. These results indicate that the contents of these endocrine-like cells appears to be differentially influenced by the feeding state of the locust.

Animals↗
PubMed1997

Localization and neurohemal release of FMRFamide-related peptides in the stick insect Carausius morosus.

FMRFamide-like immunoreactivity was localized immunohistochemically in the central stomatogastric nervous systems, visceral tissues, and the neurohemal corpora cardiaca, transverse, and segmental nerves. Each of these neurohemal areas contains one morphologically distinct type of immunoreactive neurosecretory granule. The hemolymph level of FMRFamide-like peptides, quantified by RIA, is higher in animals sampled 2 h into the dark cycle, relative to those sampled at mid-light cycle or 9 h into the dark cycle. High potassium depolarization evokes the calcium-dependent release of FMRFamide-like peptides from neurohemal areas in vitro and HPLC fractionation of hemolymph, corpora cardiaca, and their bathing medium suggests that these organs contribute a single peptide to the FMRFamide-related peptides circulating in the hemolymph of active animals.

Animals↗
PubMed1998

The effect of FMRFamide analogs on [35S]GTP-gamma-S stimulation in squid optic lobes.

Pharmacological study of Phe-Met-Leu-Phe-amide (FMRFa) receptors is hindered by the lack of selective ligands. The classification of these selective ligands is further hampered by the limited availability of functional assays. In this study, we evaluated several synthetic FMRFa analogs for agonist and antagonist activity by measuring their abilities to produce [35-S]-GTP-gamma-S stimulation or to inhibit FMRFa-induced [35S]-GTP-gamma-S binding in squid optic lobes. Analogs included acetyl-Phe-norLeu-Arg-Phe-amide (acFnLRFa), desamino-Tyr-Phe-Leu-Arg-amide (daYFLRa), desamino Tyr-Phe-norLeu-Arg-Phe-amide (daYFnLRFa), desamino Tyr-Phe-norLeu-Arg-[TIC]-amide (daYFnLR[TIC]a), desamino Tyr-Trp-norLeu-Arg-amide (daYWnLRa), (D)-Tyr-Phe-norLeu-Arg-Phe-amide (D)-YFnLRFa), Phe-Leu-Arg-Phe-amide (FLRFa), and the D-amino acid analogs of FMRFa (D-FMRFa, F-(D)-MRFa and FM-(D)-RFa). For agonist studies, full dose-response curves were generated and analyzed for potency and efficacy (maximal percent effect). FMRFamide as well as analogs ac-FnLRFa, daYFnLRFa, daYFnLR[TIC]a, D-YFnLRFa, FLRFa, and (D)-FMRFa stimulated [35S]-GTP-gamma-S binding. Analogs daYWnLRa, daYFLRa, F-(D)-MRFa, and FM-(D)-RFa failed to stimulate either [35S]-GTP-gamma-S binding or to inhibit FMRFa-induced [35S]-GTP-gamma-S binding. The rank order of potency was daYFnLRFa > or = daYFnLRF[TIC]a > acFnLRFa > (D)YFnLRFa > FLRFa > or = FMRFa >> (D)-FMRFa. The order of efficacy was daYFnLRFa = acFnLRFa = (D)-YFnLRFa > FLRFa = FMRFa > or = (D)-FMRFa > or = daYFnLRF[TIC]a. Peptide analog daYFnLR[TIC]a was less efficacious (59% maximal stimulation) than analogs daYFnLRFa, acFnLRFa, and (D)-YFnLRFa (113-146% maximal stimulation). A maximal concentration of daYFnLR[TIC]a (10 microM) reduced daYFnLRFa, acFnLRFa, and (D)-YFnLRFa induced [35S]-GTP-gamma-S stimulation, indicating that daYFnLR[TIC]a is a partial agonist at the receptor stimulated by the FMRFamide analogs. Analysis of the structural requirements needed for promoting [35S]-GTP-gamma-S binding show that elongation (i.e., daYFnLRFa, D-YFnLRFa) or modification of Phe1 (ac-FnLRFa) leads to increased efficacy and potency. Moreover, elimination of the C-terminal Phe (daYWnLRa, daYFLRa,) leads to a loss of biological activity. However, substitution with L-1,2,3,4 tetrahydroisoquinoline-3-carboxylic acid, a rigid analog of the C-terminal Phe (daYFnLR[TIC]a), leads to decreased efficacy but not loss of potency. The data suggest that immobilization or modification of the C-terminal Phe may produce highly selective and potent FMRFamide antagonists. These results agree with published receptor radioligand studies and indicate that the [35S]GTP-gamma-S assay may be useful in classifying novel FMRFamide-selective ligands.

Animals↗
PubMed1998

Mu receptor and Gi2alpha antisense attenuate [D-Met2]-FMRFamide antinociception in mice.

FMRFamide (Phe-Met-Arg-Phe-NH2) and several analogs produce centrally-mediated, naloxone-reversible antinociception, but have minimal affinity for opioid receptor (sub)types. In the present study, the antinociception in mice (55 degrees C tail-flick test) produced by supraspinal (intracerebroventricular; i.c.v.) administration of [D-Met2]-FMRFamide (a stable analog of FMRFamide) was attenuated by pretreatment with i.c.v. oligodeoxyribonucleotide antisense to the opioid mu receptor or by antisense to the Gi2alpha G-protein subunit. These data suggest that [D-Met2]-FMRFamide produces its antinociception via an opioid interneuron.

Analgesia↗
PubMed1982

Mammalian neuronal actions of FMRFamide and the structurally related opioid Met-enkephalin-Arg6-Phe7.

Since the enkephalins were first isolated a number of opioid peptides have been discovered, including a heptapeptide with the sequence Tyr-Gly-Gly-Phe-Met-Arg-Phe (Met-enkephalin-Arg6-Phe7). The heptapeptide was first isolated from chromaffin granules in bovine adrenal medulla, but using immunochemical techniques it has now been identified in human, rat and bovine brains. The C-terminal tetrapeptide of this molecule (Phe-Met-Arg-Phe) occurs in amidated form as the molluscan peptide FMRFamide. Antisera raised against FMRFamide have revealed immunoreactive material in the brains of several vertebrate species, including the rat where it occurs in nerve cell bodies and terminals. I now report that ionophoretically applied FMRFamide has an excitatory effect on rat medullary neurones which is unaffected by the opiate antagonist naloxone. In contrast, Met-enkephalin-Arg6-Phe7 and leucine-enkephalin (Leu-enkephalin) have predominantly depressant effects, which suggests that FMRFamide acts at a separate receptor.

Action Potentials↗
PubMedDate not supplied

A novel active pentapeptide from chicken brain identified by antibodies to FMRFamide.

The tetrapeptide Phe-Met-Arg-Phe-NH2 (FMRFamide) and peptides structurally related to it, have been isolated from molluscan ganglia. They have widespread actions on both invertebrate and vertebrate tissues and there is increasing evidence that they are an important group of invertebrate peptide neurotransmitters. It is of interest that the primary amino acid sequence of FMRFamide forms the C-terminal tetrapeptide of an enkephalin-like heptapeptide (Met-enkephalin-ArgPhe) isolated from bovine adrenal medulla and striatum. Antisera to FMRFamide have been shown to react in radioimmunoassay and immunohistochemistry with material in the central nervous system of various vertebrate species, but the identity of this material, and in particular its relationship to the opioid heptapeptide, remains uncertain. We have used antibodies specific for the C-terminus of FMRFamide in radioimmunoassays to monitor purification of the material in chicken brain. We describe here the sequence of one of the peptides obtained. It is a biologically active peptide which does not seem to be related to other known vertebrate neuropeptides.

Animals↗