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PubMed1986

Antibodies to FMRF amide, and the related pentapeptide LPLRF amide, reveal two groups of immunoreactive peptides in chicken brain.

A radioimmunoassay has been developed for the chicken brain peptide, Leu-Pro-Leu-Arg-Phe-amide (LPLRF amide); this peptide was originally discovered because it reacts with antibodies to the molluscan neuropeptide FMRF amide. The present antibody to LPLRF amide reacts about twenty times less well with FMRF amide compared with LPLRF amide. Using radioimmunoassays employing antibodies raised against LPLRF amide and FMRF amide we have separated by gel filtration and HPLC several different immunoreactive peptides in acid alcohol extracts of chicken brain. When LPLRF amide was used as the assay standard one group of peptides reacted similarly with the two types of antibody; the other group, which was represented by a single major component, reacted at least 50 times better with FMRF amide antibodies compared with LPLRF amide antibodies. It seems, therefore, that in the avian central nervous system, and probably other vertebrates, there are several different groups of peptides immunochemically related to FMRF amide.

Animals↗
PubMedDate not supplied

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.

FMRF-NH2-like immunoreactivity was localized in the pancreatic polypeptide containing cells of the rat islet. FMRF-NH2 was investigated with regard to its effect on insulin, somatostatin and glucagon secretion from the isolated perfused rat pancreas. FMRF-NH2 (1 microM) significantly inhibited glucose stimulated (300 mg/dl) insulin release (p less than 0.005) and somatostatin release (p less than 0.01) from the isolated perfused pancreas. FMRF-NH2 (1 and 10 microM) was without effect on glucagon secretion, either in low glucose (50 mg/dl), high glucose (300 mg/dl), or during arginine stimulation (5 mM). These findings indicate that these FMRF-NH2 antisera recognize a substance in the pancreatic polypeptide cells of the islet which may be capable of modulating islet beta and D cell activity.

Animals↗
PubMed1985

Anatomy and physiology of the neuroendocrine arcuate nucleus.

The arcuate nucleus surrounds the ventral part of the third ventricle and contains densely packed small neurons with 1-3 dendrites. At least fifteen transmitters and neuropeptides have been found in perikarya of arcuate neurons. Each transmitter and neuropeptide have a characteristic distribution. In many cases distributions overlap (for example, dopamine and somatostatin, dopamine and neurotensin, neuropeptide Y and somatostatin) and alpha-MSH and beta-endorphin seem to have identical distributions but there are also distinctive neuronal populations containing only one of the described transmitters or neuropeptides (neuropeptide Y and alpha-MSH). Studies show extensive colocalization of dopamine and neurotensin and sparse colocalization of dopamine and GABA, neuropeptide Y and FMRF-NH2 and neuropeptide Y and somatostatin. Colocalization does not seem to be the rule in the arcuate, however, it is possible that colocalization may vary with the physiological state or sex of the animal. It also should be noted that our techniques may not be sensitive enough. To study efferent projections as a possible organizing principle within the arcuate, retrograde fluorescent tracing was combined with transmitter and neuropeptide immunohistochemistry. Mainly NPY and alpha-MSH neurons were studied and both peptides are present in projections to the preoptic area as well as to the midbrain periaqueductal gray. Some arcuate neurons were found to have collateral axons to both these areas. The arcuate communicates primarily with the pituitary gland, hypothalamus, limbic system, midbrain periaqueductal gray and autonomic nuclei of the brain stem. In this way, the arcuate may be involved in integrating emotional, sensory, vegetative homeostatic and autonomic functions with endocrine functions.

Animals↗
PubMed1985

Neuropeptides in a microturbellarian--whole mount immunocytochemistry.

A whole mount immunofluorescence method was used for the localization of immunoreactivity (IR) to four regulatory peptides and the bioamine serotonin in the nervous system of Stenostomum leucops (Turbellaria, Platyhelminthes). The flatworm S. leucops belongs to the taxon Catenulida which, according to the new phylogenetic system by Ax [2], forms a key group between the coelenterates and more advanced flatworm species. Positive IR was obtained using antisera against FMRF-amide, beta-endorphin, growth hormone releasing factor (GRF), substance P, and serotonin. The distribution patterns of these neuropeptide-like immunoreactivities differ significantly from each other. Antisera against Leu-enkephalin, bovine pancreatic polypeptide (BPP), bombesin, cholecystokinin (CCK-8), neurotensin, somatostatin, growth hormone (GH), secretin, and neurophysin II gave negative results. This primitive flatworm shows similarities with hydra in the lack of IR to anti-somatostatin, anti-Leu-enkephalin, and anti-BPP. These antisera give positive IR in more advanced flatworm species, indicating a later convergent evolution of vertebrate-like peptides within the phylum Platyhelminthes.

Animals↗
PubMedDate not supplied

Biochemical characterization of FMRF-NH2-like peptides in spinal cords of various mammalian species using specific radioimmunoassays.

Phe-Leu-Phe-Gln-Pro-Gln-Arg-Phe-NH2 (F-8-F-NH2) and Ala-Gly-Glu-Gly-Leu-Ser-Ser-Pro-Phe-Trp-Ser-Leu-Ala-Ala-Pro-Gln-Arg-Phe-NH2 (A-18-F-NH2), originally detected by FMRF-NH2 antiserum and subsequently isolated from bovine brain, were found to be highly localized in the bovine spinal cord. Using specific radioimmunoassays coupled with HPLC, F-8-F-NH2 and A-18-F-NH2 immunoreactivities in spinal cord of bovine, rat, mouse, guinea pig and human were studied. One major F-8-F-NH2 immunoreactivity was detected in the spinal cord of every species except in human, however, the retention time of F-8-F-NH2 immunoreactivity appears to vary from species to species. In the human spinal cord three major F-8-F-NH2 immunoreactivities are detected and one of them was eluted in the position of F-8-F-NH2. Two major A-18-F-NH2 immunoreactivities were detected in every species except guinea pig; one of these immunoreactivities can be identified as F-8-F-NH2 immunoreactivity due to the high affinity of the A-18-F-NH2 antiserum to F-8-F-NH2. F-8-F-NH2 and A-18-F-NH2 immunoreactivities can also be clearly detected by FMRF-NH2 antiserum, however, the quantities of these peptides can be grossly underestimated by the FMRF-NH2 RIA. These results confirm that there is a novel system of FMRF-NH2-like peptides in mammalian CNS and some of them are more closely related to the bovine peptides, F-8-F-NH2 and A-18-F-NH2 than to FMRF-NH2.

Animals↗
PubMed1988

Structural aspects of gastrin/CCK-like insect leucosulfakinins and FMRF-amide.

The leucosulfakinins (LSKs), isolated from head extracts of the cockroach Leucophaea maderae, are sulfated neuropeptides with homology to gastrin and cholecystokinin. The undecapeptide LSK and decapeptide LSK-II stimulate contractions of the isolated cockroach hindgut. Several structural aspects of the two gastrin/CCK-like insect leucosulfakinins (LSKs) and their relation to FMRF-amide are discussed. Replacement of the oxidation sensitive Met residue with isosteric norleucine leads to an analog with retention of biological activity. The Arg residue of the LSKs is critical for cockroach hindgut contractile stimulatory activity, as its introduction into gastrin II transforms the inactive peptide into an active analog. As demonstrated by the equipotent [His14,Arg16]gastrin II, the His8 and Asp5 residues of LSK are not critical for activity. The common C-terminal tetrapeptide of the LSKs ([8-11]LSK) is inactive. Taken together with a comparison of the two LSK structures, the data suggest that the LSK active core resides between [8-11]LSK and [4-11]LSK. This is confirmed by considerable activity displayed by the sulfate analog of LSK-II, which contains an extra sulfate group on the Ser2 residue in the N-terminal region. Homology between the LSKs and molluscan cardioacceleratory and rectum contractile neuropeptide FMRF-amide and Met-enkephalin-Arg6-Phe7 is discussed. The insect LSKs may represent a molecular evolutionary link between the vertebrate gastrin/CCK family and this mammalian enkephalin.

Amino Acid Sequence↗
PubMedDate not supplied

One receptor type mediates two independent effects of FMRFa on neurosecretory cells of Lymnaea.

Structure activity relations (SAR) of FMRFa on the transient hyperpolarizing response and long lasting depression of excitability of neurosecretory caudo dorsal cells (CDCs) of the pond snail Lymnaea stagnalis were examined. Although these effects to FMRFa occur independently, the SARs for the induction of both responses were identical suggesting that CDCs possess a single type of FMRFa receptors. Native GDPFLRFa and SDPFLRFa were equipotent to FMRFa receptors. It is concluded that activation of the receptor requires [Arg3-Phe4]-NH2, whereas N-terminal amino acids are involved in binding.

Animals↗
PubMedDate not supplied

Peripheral injection of DNS-RFa, a FMRFa agonist, suppresses morphine-induced analgesia in rats.

The present results demonstrate an antagonistic effect of DNS-RFa on morphine-induced analgesia in rats. This confirms previous evidence presented by others on the effects of FMRFa-related peptides when applied centrally. Unlike these peptides, however, it is shown here that DNS-RFa is effective upon peripheral injection. The effects of DNS-RFa on morphine-induced analgesia were dose-dependent (ED50 = 0.5 mg/kg). DNS-RFa alone (5 mg/kg) did not affect the control level of nociception. Peripheral injection of FMRFa (5 mg/kg) did not affect morphine-induced analgesia. DNS-RFa defines the minimal configuration to activate neuronal FMRFa receptors in the pond snail. The present report suggests also that in vertebrates the Arg-Phe-NH2 sequence is essential and that DNS-RFa readily penetrates the blood-brain barrier.

Analgesia↗
PubMedDate not supplied

IgG from antiserum against endogenous mammalian FMRF-NH2-related peptides augments morphine- and stress-induced analgesia in mice.

Two mammalian FMRF-NH2-like peptides have been isolated from bovine brain; an octapeptide with the structure Phe-Leu-Phe-Gln-Pro-Gln-Arg-Phe-NH2 (F-8-F-NH2) and an octadecapeptide, Ala-Gly-Glu-Gly-Leu-Ser-Ser-Pro-Phe-Trp-Ser-Leu-Ala-Ala-Pro-Gln-Arg-Phe- NH2 (A-18-F-NH2). In the present study determinations were made of the effects of intracerebroventricular administration of IgG prepared from antisera raised against these peptides on nociception and morphine- and immobilization-induced opioid analgesia in mice. Both F-8-F-NH2-IgG and A-18-F-NH2-IgG antisera increased nociception (thermal response latency) and significantly augmented morphine- and immobilization-induced analgesia in a naloxone reversible manner, with F-8-F-NH2-IgG antisera having a greater effect than A-18-F-NH2-IgG antisera. These results provide further evidence that mammalian FMRF-NH2-like peptides function as endogenous opiate antagonists and have a role in the mediation of antinociception.

Analgesia↗
PubMedDate not supplied

Isolation of FMRFa-like peptides from the DB-containing connective tissue of Helix aspersa.

The endocrine dorsal bodies (DB) of Helix aspersa are innervated by axons from the central nervous system, which establish synapse-like structures (SLS) with the DB cells. Previous immunocytochemical studies suggested the presence of FMRFa-like substances in nerves of the DB area and in SLS. This paper reports on biochemical attempts undertaken in order to investigate the nature of these substances: the use of HPLC and RIA confirms the presence of three FMRFa-like peptides in the DB-containing connective tissue among which one is probably the FMRFa itself.

Amino Acid Sequence↗
PubMed1995

Neurotransmitter and neuropeptide modulation of high affinity choline uptake in Limulus brain.

The role of neurotransmitters in the modulation of the sodium-dependent high affinity choline uptake system (HAChUS) of the horseshoe crab, Limulus polyphemus has been investigated utilizing a tissue slice preparation. Choline uptake was significantly decreased by carbachol but unaffected by atropine and d-tubocurarine. The muscarinic agonist oxotremorine decreased choline uptake by 30.4% while the muscarinic antagonist, pirenzepine, increased uptake by 29.6%. Applied in combination, pirenzepine and oxotremorine abolished their individual effects resulting in control values for choline uptake. The non-cholinergic transmitters octopamine and serotonin significantly enhanced choline uptake. The neuropeptide proctolin elicited a 20% increase in choline transport whereas Phe-Met-Arg-Phe (FMRF) amide was without effect. This study demonstrates that neurotransmitters and neuropeptides modulate the HAChUS, possibly through specific receptor-mediated second messenger systems.

Animals↗
PubMed1994

Inhibition of Na/Ca exchange by Phe-Met-Arg-Phe-NH2 (FMRFa)-related peptides in intact rat pancreatic B-cells.

Phe-Met-Arg-Phe-NH2 (FMRFa)-related peptides were recently shown to inhibit Na/Ca exchange in cardiac sarcolemmal vesicles. In the present study, we examined the effects of FMRFa-related peptides on Na/Ca exchange in intact (pancreatic B) cells. At 2.8 mM glucose, FMRFa-related peptides only weakly inhibited Na/Ca exchange although their effect was more marked under depolarizing conditions. The peptides blocked neither the Na/K-ATPase nor Ca2+ channels but slightly reduced membrane K+ permeability. Our data indicate that FMRFa-related peptides are weak and non-specific inhibitors of Na/Ca exchange in intact B cells. The data do not confirm the view that the peptides may exert some of their physiological modulatory role by inhibiting Na/Ca exchange.

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗
PubMed1990

Inhibitory modulation of neuronal voltage-dependent sodium current by Phe-Met-Arg-Phe-amide.

The tetrodotoxin (TTX)-sensitive, voltage-gated Na(+)-current (INa) in a cluster of peptidergic neurons, involved in egg laying, in the CNS of the mollusc Lymnaea stagnalis, is modulated by the neuropeptide FMRFa (Phe-Met-Arg-Phe-NH2). Application of FMRFa reversibly reduced the isolated INa in a dose-dependent fashion. The physiological consequence is that the threshold for action potential generation is increased, causing an arrest of ongoing firing activity. The inhibitory action of FMRFa reported here is the first known example of modulation of the voltage-gated INa by a putative neurotransmitter in intact nerve cells. This finding underlines the importance of modulation of ionic currents as a mechanism of regulation of neuronal excitability and includes the voltage dependent Na current in the range of currents subject to transmitter modulation.

Animals↗
PubMed1990

Pericardial peptides enhance synaptic transmission and tension in phasic extensor muscles of crayfish.

Two identified peptides, which are structurally related to FMRF-NH2 and are known to be associated with lobster pericardial organs, increase nerve-evoked tension and excitatory postsynaptic potentials (EPSPs) recorded from crayfish deep abdominal extensor muscles. At low stimulus frequencies, which produce marked depression of muscle twitches with successive stimuli, the peptides quickly and reversibly restore tension. Increased quantal content of transmitter release, rather than changes in postsynaptic input resistance, accounted for most of the increase in EPSP amplitude. The results support earlier suggestions that these two peptides may act as circulating neurohormones and provide the first evidence for peptidergic modulation of a phasic neuromuscular system in a crustacean.

Animals↗
PubMed1991

IgG from neuropeptide FF antiserum reverses morphine tolerance in the rat.

Previous studies suggest that neuropeptide FF (NPFF) plays a role in opiate dependence and subsequent abstinence syndrome. The present study assessed the role of NPFF in opiate tolerance. Third ventricular injection of IgG from NPFF antiserum restored the analgesic response to i.c.v. morphine in morphine-tolerant rats (radiant heat tail flick test). IgG from control serum failed to produce this effect. In opiate-naive rats, however, the same treatment with IgG from NPFF antiserum did not affect the analgesic response to i.c.v. morphine. Thus, immunoneutralization of NPFF appears to selectively restore morphine sensitivity in opiate-tolerant animals. These results support the hypothesis that endogenous NPFF contributes to opiate tolerance.

Amino Acid Sequence↗
PubMed1992

Neuropeptide FF is colocalized with catecholamine-synthesizing enzymes in neurons of the nucleus of the solitary tract.

Neuropeptide FF (NFF) is an amidated octapeptide of bovine origin. It has some antiopioid-like effects and it elevates blood pressure when injected intravenously in rats. NFF-immunoreactive nerve cells and terminals are localized in large numbers in the dorsomedial caudal brainstem which is a region involved in central regulation of blood pressure. We compared the localization of NFF-immunoreactive neurons with medullary catecholamine-synthesizing neurons by using immunohistochemical double-labeling and light microscopic mirror methods. NFF and tyrosine hydroxylase coexisted in a minor portion of the NFF neurons in the nucleus of the solitary tract and occasional cell bodies were stained with both NFF and PNMT (phenylethanolamine N-methyltransferase) antisera. The results have anatomical correlation with previous pharmacological reports, suggesting that NFF is present in neuronal systems involved in cardiovascular reflex arcs.

Animals↗
PubMed1993

FMRF-amide modulates the electrical activity of the leech Retzius cell.

The effect of the peptide FMRF-amide on the electrical activity of the leech Retzius (R) cell was investigated using electrophysiological techniques. FMRF-amide and six structurally related analogs increased the excitability of the R cell in several distinct ways that could act in concert to modulate transmitter release. 'Puffs' of FMRF-amide transiently depolarized the cell leading to a barrage of action potentials. This depolarization was followed by a phase of rhythmical bursting that appeared intrinsic to the neuron. FMRF-amide also broadened the plateau of the Ca(2+)-dependent action potential. The results suggest that the terminal Phe and Arg as well as the C-terminal amide are critical for the activity of these peptides.

Action Potentials↗
PubMed1996

Nervus terminalis projection to the retina in the 'four-eyed' fish, Anableps anableps.

The eye of the surface dwelling 'four-eyed' fish, Anableps possesses an aquatic and an aerial optical system. The aerial system is strongly hyperopic when the animal dives, i.e. during mating, and the dorsal pupil is submerged. We studied the retino-petal nervus terminals projection to the aerial and to the aquatic retina by Phe-Met-Arg-Phe-NH2 (FMRF) immunocytochemistry and found both to be equally innervated. This finding sheds doubt on the proposed functional significance of this projection for reproductive behaviour.

Animals↗