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PubMed1992

The effects of FMRFamide, 5-hydroxytryptamine and phorbol esters on the heart of the mussel Geukensia demissa.

The ventricle of the mussel Geukensia demissa is inhibited by 5-hydroxytryptamine and excited by the molluscan neuropeptide FMRFamide. Supra-threshold doses of amide result in marked positive chronotropy and inotropy within 5-15 s. 5-Hydroxytryptamine at 10(-8) M produces diastolic arrest within 10 s. A 1-min exposure to FMRFamide (5 x 10(-8) M) results in a small increase in the cytoplasmic levels of adenosine 3',5'-cyclic monophosphate; shorter or longer exposures have no effect. The cAMP content of ventricles incubated in 5 x 10(-8) M 5-hydroxytryptamine for 1 min decreases by 2.3 pmol/mg protein; longer or shorter incubations have no effect. Treatment with forskolin results in 3- or 4-fold increases in adenosine 3',5'-cyclic monophosphate, but forskolin has no effect on the mechanical activity of the ventricle. The levels of inositol monophosphate, inositol 1,4-diphosphate, and inositol 1,4,5-triphosphate in tissues exposed to 5-hydroxytryptamine are not different from levels in control tissues. FMRFamide decreases the levels of these phosphoinositides by 50% or more. Lower concentrations of phorbol 12,13-diacetate (10(-8) to 10(-7) M) and phorbol 12-myristate,13-acetate (10(-6) M) cause positive chronotropy in the isolated ventricle; higher concentrations induce systolic arrest. These results suggest that the effects of 5HT on the ventricle are not mediated by adenosine 3',5'-cyclic monophosphate or inositol 1,4,5-triphosphate. The effects of FMRFamide may involve a decrease in inositol 1,4,5-triphosphate. The effects of amide may involve a decrease in inositol 1,4,5-triphosphate. The response of the ventricles to phorbol esters suggest that protein kinase C may be involved in the regulation of cardiac contractility.

Animals↗
PubMed1994

Localization of FMRFamide- and ACEP-1-like immunoreactivities in the nervous system and heart of a pulmonate mollusc, Achatina fulica.

Immunohistochemical localization of two neuropeptides possibly involved in the regulation of cardiac activity in a pulmonate mollusc, Achatina fulica Férussac, was studied. On the ventral surface of the right cerebral ganglion, more than 50 neurons with diameters of 30-50 microns showed immunoreactivity to the antiserum of the neuropeptide FMRFamide. Many were also immunoreactive to an antiserum raised against Achatina cardio-excitatory peptide-1 (ACEP-1). Although FMRFamide-like immunoreactive neurons occurred in all components of the subesophageal ganglia, identifiable ACEP-1-like immunoreactive neurons were located only in the visceral ganglion and the right parietal ganglion. In the heart, FMRFamide- and ACEP-1-like immunoreactive fibers were restricted to the atrium and the aortic end of the ventricle, consistent with morphological observations of cardiac innervation. The present results suggest that FMRFamide- and ACEP-1-like peptides are involved in regulating the heart beat of this snail.

Animals↗
PubMed1984

A critical examination of the occurrence of FMRFamide immunoreactivity in the brain of guinea pig and rat.

Several reports (cf. Weber et al. (1981) Science 214:1248-1251) have described the extensive occurrence, in rat brain, of material immunologically related to the molluscan neuropeptide FMRFamide. We have reexamined these data in guinea pig and rat, using six different antisera to FMRFamide. Immunoreactive perikarya and fibres were found to be distributed throughout the rodent brain (Table 1). This distribution was roughly similar to that found by Weber and coworkers. However, solid-phase absorption of the antisera with bovine pancreatic polypeptide, which shares an arginine and an amidated aromatic amino acid (RYamide) with FMRFamide, showed that staining in most regions could be due to crossreactivity with bovine pancreatic polypeptide-like (or neuropeptide Y-like) material. Double-labelling experiments with antisera to FMRFamide and bovine pancreatic polypeptide led to the same conclusion. The only structures where no apparent crossreactivity occurred were perikarya and fibres in the nucleus dorsomedialis, ventromedialis, periventricularis and paraventricularis hypothalami and fibres in the area lateralis hypothalami, nucleus parabrachialis, substantia grisea centralis mesencephali, various parts of the formatio reticularis, and spinal cord. Hence only these structures might contain material which is more related to the molluscan tetrapeptide.

Animals↗
PubMed1994

Peripheral connections of FMRFamide-like immunoreactive neurons in the snail, helix pomatia: an immunogold electron microscopic study.

Using a postembedding immunogold electron microscopic method, the ultrastructure and synaptic connections of FMRFamide-like immunoreactive varicosities were investigated in different peripheral organs of the snail Helix pomatia, including the heart (auricle), intestine, hepatopancreas, upper tentacle and salivary gland. The FMRFamide-like immunoreactive varicosities contained granules and vesicles as described in a previous study of the CNS of this species, and additionally, based on their granule content, two novel types of varicosities were found in the auricle. A selective accumulation of gold particles over the granules could be demonstrated. The FMRFamide-like immunoreactive varicosities formed unspecialized contacts with postsynaptic target cells in all peripheral organs investigated, with the exception of the tentacle retractor muscle. Both the neuro-muscular and the neuro-glandular contacts were characterized by either unspecialized close apposition of the 'pre- and postsynaptic' membranes or the immunoreactive elements faced the target cell(s) across a relatively wide extracellular space. In the tentacle retractor muscle some of the neuromuscular contacts showed appositions of electron dense material along the presynaptic membrane, clustering of agranular synaptic vesicles and intersynaptic cleft material. The present observations support previous electrophysiological findings and suggest a versatile modulatory role of FMRFamide and related substances in the Helix PNS.

Animals↗
PubMed1996

Transient and sustained expression of FMRFamide-like immunoreactivity in the developing nervous system of Lymnaea stagnalis (Mollusca, Pulmonata).

1. In the present study we have investigated the ontogeny of FMRFamide expression in the snail, Lymnaea stagnalis, from its first appearance to its distribution in young adults. 2. The first FMRFamide-like immunoreactive (FaLI) cells within CNS appear by E45 embryonic stage (premetamorphic veliger). The number of FaLI neurons increases throughout both pre- and post-hatching development. 3. Both transient and sustained expression of FMRFamide-like immunoreactivity by specific sets of neurons occurs. Two cells which transiently express immunoreactivity appear outside the future CNS by the stage E45. Other population of transient FaLI neurons includes bilaterally symmetric groups of cells in the cerebral and pedal ganglia during posthatching stages P1 (hatchlings) to P5 (juveniles). All other immunostained cells which appear during development maintain their transmitter phenotype into adulthood. 4. The possible role of FMRFamide-related peptides in the processes of morpho- and neurogenesis is discussed.

Animals↗
PubMed2003

Expression of FMRFamide gene encoded peptides by identified neurons in embryos and juveniles of the pulmonate snail Lymnaea stagnalis.

Immunoreactivity to antibodies (ABs) against FMRFamide, CARP, and three FMRFamide gene encoded peptides, i.e., EFLRIamide, the non-FMRFamide peptide "SEEPLY," and the 35-amino-acid "acidic peptide," were investigated in developing embryos and juveniles of Lymnaea stagnalis. Five early transient embryonic neurons revealed immunoreactivity to EFLRIamide. One of the early neurons, the central posterior, also expressed SEEPLY and CARP immunoreactivity. Two neurons in the anlage of the left and right parietal ganglia coexpressed immunoreactivity to EFLRIamide (type 1 transcript) and acidic peptide (type 2 transcript). Within the developing ganglia altogether 30 neurons expressed the type 1 transcript, and three expressed the type 2 transcript. No peripheral cells immunoreactive to SEEPLY or acidic peptide ABs were found, whereas bipolar EFLRIamide- and CARP-immunoreactive cells were abundant in the lip, mantle and foot. After hatching, the number of immunoreactive neurons in ganglia increased up to 223 and the neurons expressing tetrapeptides were dominant (91%). No neurons coexpressing type 1 transcript and type 2 transcript could be detected in juveniles and adults. At this time, an extensive innervation is developed in the periphery, including foot, mantle, buccal mass, salivary glands and alimentary tract, established mainly by EFLRIamide-immunoreactive cells and varicose fibers of extrinsic and intrinsic origin. It is suggested that both sensory and regulatory function can be attributed to the FMRFamide gene encoded tetrapeptides throughout embryonic and juvenile development in Lymnaea, whereas heptapeptides are presumed to play a modulatory role.

Animals↗
PubMed2000

Mosaic arrangement of SCP(B-), FMRFamide-, and histamine-like immunoreactive sensory hair cells in the statocyst of the gastropod mollusc Pleurobranchaea japonica.

A pair of statocysts are located in the periganglionic connective tissue of the pedal ganglia of the opisthobranch mollusc Pleurobranchaea japonica. Light- and electron-microscopic observations show that the sensory epithelium of the statocyst consists of 13 disk-shaped hair cells. Each hair cell sends a single axon to the cerebral ganglion through the static nerve. Neurotransmitters in the hair cells were examined by means of immunocytochemistry. Our results show that the 13 sensory hair cells include two SCPB-, three FMRFamide-, and eight histamine-like immunoreactive cells. One hair cell contains a transmitter substance other than SCPB-, FMRFamide, histamine, serotonin, or GABA. One of the two SCPB-like immunoreactive cells, located in the ventral region of the statocyst, is the largest cell in the statocyst. The other, located in the anterodorsal region, shows co-immunoreactivity to both SCPB and FMRFamide antisera. Among the three FMRFamide-like immunoreactive hair cells, one is located in the posteroventral region, separated from the other two, which are adjacent to each other in the anterodorsal region. All the eight histamine-like immunoreactive hair cells are adjacent to one another, occupying the remainder of a triangular pyramid-shaped region. These immunoreactive cells are symmetrically placed in the right and left statocysts. This mosaic arrangement was identical among specimens. Thus the static nerve may code information about position or movement of the statoliths, with the use of different transmitters in the mosaic arrangement of the hair cells.

Animals↗
PubMed1997

Distribution of FMRFamide-like immunoreactivity in the nervous system of Lumbricus terrestris.

The distribution of FMRFamide-like immunoreactive cell bodies and fibers in the nervous system of the earthworm Lumbricus terrestris has been studied by means of immunocytochemistry. The cerebral ganglion contains 150-170 immunoreactive nerve cells that are organized into six major groups in the rostral and five major groups in the caudal part of the ganglion; 160-180 immunoreactive nerve cells are present in the subesophageal ganglion, and 80-90 in the ventral cord ganglia. Immunoreactive neurons of the subesophageal and the ventral cord ganglia show similar distributions, in that FMRFamide-like immunoreactive cells form a ventromedial and a lateral cell group. Neuropil in all parts of the central nervous system shows intensively stained varicose and non-varicose fibers. Each segmental nerve contains FMRFamide-like immunoreactive fibers that can partly be traced to the two muscle layers of the body wall, and a fine immunoreactive network lies among the muscle fibers. A similar network is found in the wall of the alimentary canal. Immunopositive perikarya and fibers have been detected in the prostomial nerves, in the stomatogastric system. Some epithelial cells of the body wall are also immunopositive. The morphological characteristics and localization of FMRFamide immunoreactive neurons suggest that they may be involved in: (1) central integratory processes; (2) neuromuscular regulation in both the body wall and enteric system; (3) sensory processes.

Animals↗
PubMed1983

FMRFamide-like immunoreactivity in rat brain: development of a radioimmunoassay and its application in studies of distribution and chromatographic properties.

A radioimmunoassay is described for the molluscan neuropeptide, Phe-Met-Arg-Phe-NH2 (FMRFamide). The antibody used is C-terminal-specific and shows slight but significant (1-2%) cross-reactivity with chicken pancreatic polypeptide (APP). The assay has been used to identify in rat brain extracts a pair of molecules that may represent mammalian counterparts of FMRFamide. Their concentrations were highest in spinal cord and hypothalamus (greater than 10 pmol . g-1) and lowest in cerebellum and striatum (less than 3.5 pmol . g-1). The two immunoreactive peptides were separated on CM ion-exchange chromatography where they appeared to be less basic than FMRFamide. On Sephadex G50 gel filtration one eluted in a similar position of FMRFamide and the other slightly earlier suggesting it may be of higher molecular weight. The rat immunoreactive components do not correspond to previously described neuropeptides or hormones, and may be members of a new group of mammalian neuropeptides with transmitter or modulatory functions.

Animals↗
PubMed1986

Inhibitory influences of FMRFamide and PLG on stress-induced opioid analgesia and activity.

The effects of i.c.v. administration of the peptide FMRFamide (Phe-Met-Arg-Phe-NH2), as well as i.p. injections of PLG (Pro-Leu-Gly-NH2) and the opiate antagonist, naloxone, on immobilization-induced analgesia and locomotor activity were examined in CF-1 and C57BL strains of mice. Both naloxone (1.0 mg/kg) and FMRFamide (0.10-1.0 microgram) blocked the experimentally induced analgesia and activity, whereas PLG (0.10-10 mg/kg) suppressed only analgesia. These results indicate that FMRFamide (or FMRFamide-like neuropeptides) and PLG may function as differential antagonists of the behavioral and physiological consequences of endogenous opioid activation.

Animals↗
PubMed1987

Calcium channel blockers inhibit the antagonistic effects of Phe-Met-Arg-Phe-amide (FMRFamide) on morphine- and stress-induced analgesia in mice.

Determinations were made of the effects of the calcium channel blockers, nifedipine and verapamil, on the antagonistic effects of FMRFamide (Phe-Met-Arg-Phe-NH2) and naloxone on morphine- and immobilization-induced opioid analgesia in mice. Intraperitoneal (i.p.) administrations of the calcium channel antagonists significantly reduced the inhibitory effects of intracerebroventricular (i.c.v.) FMRFamide, but had no effects on i.p. or i.c.v. naloxone-mediated inhibition of either morphine- or immobilization-induced analgesia. These results suggest that the antagonistic effects of FMRFamide, (or other endogenous FMRFamide-like peptides) on both opiate- and opioid-mediated analgesia in mice may involve alterations in the functioning of calcium channels.

Animals↗
PubMed1995

Stereochemistry of the Aplysia neuronal 12-lipoxygenase: specific potentiation of FMRFamide action by 12(S)-HPETE.

Nervous tissue of the marine mollusc, Aplysia californica, generates arachidonic acid metabolites in response to neurotransmitters such as histamine or FMRFamide. In addition, identified neurons of Aplysia respond to the pharmacologic application of some of these products, particularly those of the 12-lipoxygenase pathway. We investigated the chirality of the initial Aplysia 12-lipoxygenase product, 12-HPETE, in preparation for more detailed metabolic studies and for the analysis of the physiological activity of the endogenous lipid. Neural homogenates and intact ganglia exclusively generate 12(S)-HPETE as do the better characterized mammalian lipoxygenases. The direct application of 12(S)-HPETE to cultured sensory neurons induced a hyperpolarization which averaged 2.6 mV. We did not find any difference between the response to the naturally-occurring 12(S)-HPETE and its diastereomer, 12(R)-HPETE which is not generated in Aplysia. Both isomers were significantly more effective than 15(S)-HPETE. In contrast, 12(S)-HPETE, but not 12(R)-HPETE, was a potent modulator of the action of the molluscan neuropeptide, FMRFamide. Prior application of 12(S)-HPETE to cultured sensory neurons increased the subsequent response to a submaximal dose of FMRFamide by 60%. On the other hand, 12(R)-HPETE reduced the subsequent response to the peptide by 30%. The lack of stereospecificity in the direct effect of the lipids differs markedly from their stereospecific effects as modulators of FMRFamide action. This suggests that there may be an important neurophysiologic role for these lipid modulators which is distinct from their direct effects, and also indicates that there are multiple sites and mechanisms by which lipid hydroperoxides act on neurons in Aplysia.

Animals↗
PubMed1982

The molluscan neuropeptide FMRFamide: calcium-dependent release and blood levels in Macrocallista (Bivalvia).

Ganglia dissected from the marine bivalve, Macrocallista nimbosa, were pooled and incubated in a series of seawater media designed to promote or inhibit the release of the neuropeptide Phe-Met-Arg-Phe-NH2 (FMRFamide). The amount of peptide released, determined by radioimmunoassay (RIA), was enhanced two to seven times when the medium contained high potassium. FMRFamide released was reversibly inhibited when calcium was omitted from the high potassium medium. Immunoreactive FMRFamide was found in Macrocallista hemolymph in a concentration (10(-9)M) that excites isolated Macrocallista ventricles. Although the in vivo release sites have not yet been localized, these findings already show that the endogenous neuropeptide FMRFamide can be characterized as a neurohormone or as a neurotransmitter in Macrocallista.

Animals↗
PubMed1985

FMRFamide, a putative endogenous opiate antagonist: evidence from suppression of defeat-induced analgesia and feeding in mice.

Social conflict and defeat in mice leads to an activation of endogenous opiate systems. The effects of intracerebroventricular administration of the peptide FMRFamide (Phe-Met-Arg-Phe-NH2) and the opiate antagonist naloxone, on aggressive encounters, defeat-induced analgesia and defeat-induced feeding were examined in male mice. Both substances reduced the number of bites required to cause defeat in subordinate mice during aggressive encounters, as well as suppressing the subsequent defeat-induced analgesia. Administration of FMRFamide or naloxone also reduced defeat-induced feeding. These results indicate that FMRFamide (or FMRFamide-like neuropeptides) may function as endogenous opioid antagonists.

Analgesia↗
PubMedDate not supplied

Amnesic action of FMRFamide in rats.

The effects of FMRFamide on passive avoidance behaviour and electroshock-induced amnesia following intracerebroventricular administration were studied in rats. FMRFamide given immediately after the learning trial, or 20 min before the retention trial, attenuated the avoidance response, thereby impairing the consolidation and retrieval processes. Electroshock induced amnesia when applied immediately after the learning trial. Treatment with FMRFamide facilitated the amnesia of the passive avoidance response. The results indicate that FMRFamide peptide belongs in the class of neuropeptide which are amnesic.

Amnesia↗
PubMed1994

Anxiolytic effect of neuropeptide FMRFamide in rats.

Central administration of FMRFamide in rats dose dependently increased the duration of time spent in the open arm of an elevated plus maze and enhanced the number of drink contacts in the thirsty rat conflict test. Similarly in the social interaction test, animals pretreated with FMRFamide spent sufficient time in active social interaction as compared to controls. Neuropeptide FMRFamide antagonized the anxiogenic effect of yohimbine and enhanced the antianxiety effect of diazepam in rats. The results indicate anxiolytic action of FMRFamide and the mechanism of such an action may involve serotonergic transmission.

Amino Acid Sequence↗
PubMed1988

FMRFamide prevents habituation and potentiates the gill withdrawal reflex in the isolated gill preparation of Aplysia.

Perfusion of the endogenous neuropeptide, FMRFamide, through the isolated gill of Aplysia facilitated the amplitude of the gill withdrawal reflex (GWR) evoked by tactile stimulation of the gill. The GWR was facilitated in a dose-dependent manner. The facilitation of the GWR produced by FMRFamide perfusion was reversible. In addition to facilitating GWR amplitude, FMRFamide perfusion could also prevent habituation of the reflex. It is hypothesized that FMRFamide may play a role in the peripheral nervous system (PNS) in the gill in the mediation of behavioral state and modulation of adaptive gill behaviors.

Animals↗
PubMed1989

The molluscan neuropeptide FMRFamide stimulates the release of [14C]acetylcholine from isolated ileal synaptosomal preparations of guinea-pig.

FMRFamide stimulated, in a dose-dependent manner, the efflux of [14C]acetylcholine (ACh) from isolated synaptosomes of guinea-pig ileum preloaded with labelled choline. Participation of the cholinergic mechanism and/or substance P was ruled out by the finding that antagonists failed to affect the FMRFamide-induced release of ACh. The ACh-releasing action of FMRFamide was negated by the deletion of calcium ion from the bathing medium and it was also abolished by tetrodotoxin. The results obtained suggest that FMRFamide possesses the ability to induce the release of ACh from enteric synaptosomes of guinea-pig.

Acetylcholine↗