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PubMed2004

Multilevel inhibition of feeding by a peptidergic pleural interneuron in the mollusc Lymnaea stagnalis.

The pleural interneuron PlB is a white neuron in the pleural ganglion of the snail Lymnaea. We test the hypothesis that it inhibits neurons at all levels of the feeding system, using a combination of anatomy, physiology and pharmacology. There is just one PlB in each pleural ganglion. Its axon traverses the pedal and cerebral ganglia, running into the buccal ganglia. It has neuropilar branches in the regions of the cerebral and buccal ganglia where neurons that are active during feeding also branch. Activation of the PlB blocks fictive feeding, whether the feeding rhythm occurs spontaneously or is driven by a modulatory interneuron. The PlB inhibits all the neurons in the feeding network, including protraction and retraction motoneurons, central pattern generator interneurons, buccal modulatory interneurons (SO, OC), and cerebral modulatory interneurons (CV1, CGC). Only the CV1 interneuron shows discrete 1:1 IPSPs; all other effects are slow, smooth hyperpolarizations. All connections persist in Ca(2+)/Mg(2+)-rich saline, which reduces polysynaptic effects. The inhibitory effects are mimicked by 0.5 to 100 micromol l(-1) FMRFamide, which the PlB soma contains. We conclude that the PlB inhibits neurons in the feeding system at all levels, probably acting though the peptide transmitter FMRFamide.

Action Potentials↗
PubMed2003

Transmitter contents of cells and fibers in the cephalic sensory organs of the gastropod mollusc Phestilla sibogae.

While the central ganglia of gastropod molluscs have been studied extensively, relatively little is known about the organization and functions of the peripheral nervous system in these animals. In the present study, we used immunohistochemical procedures to examine the innervation of the rhinophores, oral tentacles and region around the mouth of the aeolid nudibranch, Phestilla sibogae. Serotonin-like immunoreactivity was found in an extensive network of efferent projections apparently originating from central neurons, but was not detected within any peripheral cell bodies. In contrast, large numbers of peripheral, and presumably sensory, somata exhibited reactivity to an antibody raised against tyrosine hydroxylase (the enzyme catalyzing the initial step in the conversion of tyrosine into the catecholamines). Additional tyrosine hydroxylase-like immunoreactivity was detected in afferent fibers of the peripheral cells and in several cells within the rhinophoral ganglia. The presence of serotonin, dopamine and norepinephrine in the rhinophores, tentacles and central ganglia was confirmed using high-performance liquid chromatography. Finally, FMRFamide-like immunoreactivity was detected in cells and tangles of fibers found within the rhinophore, possibly revealing glomerulus-like structures along olfactory pathways. FMRFamide-like immunoreactivity was also found in somata of the rhinophoral ganglia, in a small number of cells located in the body wall lateral to the tentacles and in what appeared to be varicose terminals of efferent projections to the periphery. Together, these results indicate several new features of the gastropod peripheral nervous system and suggest future experiments that will elucidate the function of the novel cells and innervation patterns described here.

Animals↗
PubMed1986

Peptidergic modulation of a neuromuscular junction in Aplysia: bioactivity and immunocytochemistry.

Three endogenous peptides were assayed for bioactivity at an Aplysia neuromuscular junction. Evoked contractions were enhanced by Phe-Met-Arg-Phe-NH2 (FMRFamide) and suppressed by arginine vasotocin; small cardioactive peptide B (SCPB) also enhanced contractions at low concentrations, but caused suppression at higher doses. In accordance with their putative roles as neuromodulators, immunocytochemistry revealed FMRFamide-like and SCPB-like fibers on the muscle surface.

Animals↗
PubMed1994

Localization of molluscan R15 alpha 2 peptide immunoreactivity in the mammalian brain.

The R15 neuropeptides have been identified in the marine mollusc Aplysia californica. They compose a new family of neuropeptides acting on the cardiovascular, digestive, respiratory, reproductive and nervous systems. In this report we show that one of the members of the R15 neuropeptide family, the alpha 2 peptide is conserved in lower mammals. We have identified R15 alpha 2 immunoreactive neurons in the neurosecretory cell groups of the hypothalamus and in the brainstem of the hedgehog (Erinaceus europaeus). The majority of labeled cells were localized to the anterior periventricular part of the paraventricular nucleus and the accessory neurosecretory cell groups in the lateral hypothalamus as well as to the dorsal part of the nucleus tractus solitarii. In the paraventricular nucleus, R15 alpha 2 immunoreactive neurons also exhibit immunoreactivity for oxytocin, corticotropin releasing factor, vasoactive intestinal polypeptide and for the FMRFamide-related peptide which we found to be conserved in the hedgehog brain as well. No complete colocalization of R15 alpha 2 with any of the neuroactive substances tested, is observed. The highest degree of coexistence occurs with FMRFamide-related peptide, followed by vasoactive intestinal polypeptide, oxytocin and corticotropin releasing factor.

Amino Acid Sequence↗
PubMed1982

Blood pressure elevation in rats by peripheral administration of Tyr-Gly-Gly-Phe-Met-Arg-Phe and the invertebrate neuropeptide, Phe-Met-Arg-Phe-NH2.

Phe-Met-Arg-Phe-NH2 (FMRFamide), injected at less than 1 mumol/kg intravenously in the anesthetized rat, produces sharp elevations of blood pressure and changes in respiration. The effects were dependent on the carboxyterminal Arg-Phe (RF) configuration and were stereospecific for these two amino acids. A related peptide with RF carboxyterminus, gamma 1-melanotropic stimulating hormone, also had potent blood pressure stimulating activity. The mechanisms underlying the pressor effect of FMRFamide have not yet been established but this pressor action was not significantly attenuated by standard pharmacologic antagonists or prevented by removal of the adrenal or pituitary gland.

Animals↗
PubMed1994

Immunocytochemical localization of neuropeptide F-immunoreactivity in the circumoesophageal ganglia of the gastropod mollusc, Helix aspersa using electron microscopy.

Neuropeptide F (NPF)-immunoreactivity has been localized by electron microscopy in the central nervous system of the gastropod mollusc, Helix aspersa using a region-specific antiserum in conjunction with post-embedding immunogold labelling. The specific antiserum employed, designated NPF3, was raised to a synthetic N-terminal fragment of H. aspersa NPF. Gold-labelling revealed that NPF-immunoreactivity was found almost exclusively over the contents of dense-cored secretory vesicles within nerve axons in both cerebral and subesophageal ganglia. Double-labelling of NPF and FMRFamide demonstrated no apparent co-localization in the paired cerebral ganglia. Instead, immunoreactivities of the two neuropeptides were found to have distinct locations within the ganglia. These findings suggest that NPF may be an important neuroregulator in H. aspersa and that in the cerebral ganglia it may be anatomically-distinct from FMRFamide and related peptides.

Amino Acid Sequence↗
PubMed1996

Migration of GnRH-immunoreactive neurons from the olfactory placode to the brain: a study using avian embryonic chimeras.

Previous studies suggest that gonadotropin-releasing hormone (GnRH) neurons appear in the olfactory placode and subsequently migrate into the brain during embryonic development. The aim of the present study was to obtain direct evidence for migration of GnRH neurons from the olfactory placode into the brain. Olfactory placodes from quail embryos were transplanted isotopically and isochronically, to replace the unilaterally ablated olfactory placodes of chick embryos. The chimeric embryos were allowed to develop for several days until they reached the embryonic stages when GnRH neurons are seen in the brain in normal embryos. Quail olfactory epithelia were formed in the host chick embryos. Quail olfactory nerves were also formed and reached the olfactory bulb or primordial olfactory bulb. GnRH-immunoreactive cells of quail origin revealed by a triple staining method were observed in the quail olfactory epithelium, quail olfactory nerve, chick olfactory bulb, and septo-preoptic area. These results indicate that GnRH neurons originate in the olfactory placode and migrate into the telencephalon including the septo-preoptic area. A migratory route of GnRH neurons was well documented by the use of a quail neuron-specific antibody, QN. The migratory route in the brain is discussed with special reference to the terminal nerve. A GnRH-immunoreactive neuronal group of chick origin appeared in the diencephalon of chimeric embryos. These diencephalic neurons may be of non-placodal origin. FMRFamide-immunoreactive neurons of quail origin were also found in the quail olfactory nerve and the host olfactory bulb, suggesting that FMRFamide neurons also originate in the olfactory placode and migrate into the brain.

Animals↗
PubMed1985

Arg-Phe-amide-like peptides in the primitive nervous systems of coelenterates.

By using immunocytochemistry and radioimmunoassays, several substances resembling vertebrate or invertebrate neuropeptides have been found in the nervous systems of coelenterates. The most abundant neuropeptides were those related to the molluscan neuropeptide Phe-Met-Arg-Phe-amide (FMRFamide). Of antisera against different fragments of FMRFamide, those against RFamide were superior in recognizing the coelenterate peptide. Incubation of whole mounts with these RFamide antisera visualized the coelenterate nervous system in such a detail as has previously not been possible. By using a radioimmunoassay with a RFamide antiserum and [J-125]-YFMRFamide as tracer, the RFamide-like peptide from sea anemones was isolated. After cation-exchange chromatography, gelfiltration and HPLC, this peptide was obtained in a pure form.

Animals↗
PubMedDate not supplied

Identification of RFamide neuropeptides in the medicinal leech.

Using a four-step reverse phase HPLC separation and RIA, five RFamide peptides were purified from CNS extracts of the leech Hirudo medicinalis. YMRFamide, FMRFamide, YLRFamide, FLRFamide, and GGKYMRFamide were identified by a combination of antiserum specificity in RIA, Edman degradation, and mass spectrometry. At least three of these five endogenous peptides can modulate neuromuscular interactions in the leech (38). FMRFamide-like immunoreactivity was selectively released from neural processes on isolated heart tubes in the presence of calcium and depolarizing levels of potassium.

Amino Acid Sequence↗
PubMedDate not supplied

Isolation of the neuropeptide SALMFamide-1 from starfish using a new antiserum.

We have raised antisera in rabbits to a conjugate of thyroglobulin and Lys-Tyr-Ser-Ala-Leu-Met-Phe-NH2 (KYSALMFamide), a synthetic analog of the starfish neuropeptide S1 (Gly-Phe-Asn-Ser-Ala-Leu-Met- Phe-NH2). The sensitivity and specificity of two antisera (BL and SL) for S1 were established by testing the ability of S1 and structurally related peptides (SALMFamide-2 and various FMRFamide-related peptides) to displace iodinated KYSALMFamide from the serum antibodies in an RIA. Both antisera are sensitive to femtomolar amounts of S1. BL is highly specific for S1 but SL is not, since it is also able to detect femtomolar amounts of the FMRFamide-related peptides. We have used the BL antiserum in the RIA to monitor the purification of S1 immunoreactivity from radial nerve cord extracts of both Asterias rubens and Pycnopodia helianthoides. The partial amino acid sequence GFNSALM was obtained from automated Edman degradation sequencing of pure immunoreactive peaks from both species.

Amino Acid Sequence↗
PubMed1987

Diversity in neurohaemal organs for homologous neurosecretory cells in different insect species as demonstrated by immunocytochemistry with an antiserum to molluscan cardioexcitatory peptide.

Neurosecretory cells were histochemically identified in the thoracic ganglia of the Colorado potato beetle and Drosophila melanogaster with an antiserum to the molluscan cardioexcitatory neuropeptide FMRFamide (Phe-Met-Arg-Phe-NH2). These cells and the FMRFamide-immunoreactive neurosecretory cells identified in a locust are most likely homologous. The neurosecretory axon terminals in the 3 species use different neurohaemal organs. Such a structural diversity in release sites of apparently homologous neurosecretory cells in different species may account for the large structural variability in neurohaemal organs in insects in general.

Animals↗
PubMed1995

Complex avoidance behaviour and its neurochemical regulation in the land snail Cepaea nemoralis.

1. In hot plate experiments, the pulmonate land snail Cepaea nemoralis displays a biphasic passive/active avoidance behaviour composed of retraction and subsequent searching mediated by antagonistic muscular systems. The switch, between the behaviours, is under neuronal control. 2. Leu- and met-enkephalin, as well as FMRFamide-antiserum, attenuated the retraction response and potentiated the searching behaviour. Opposite effects were achieved by injection of antisera to the enkephalins. 3. Both retraction and searching behaviours were potentiated by 5-HT. Methysergide antagonized the effects of the enkephalins on the searching behaviour. 4. We conclude that endogenous opioids act antagonistic to FMRFamide in the neuronally controlled switch between passive and active avoidance behaviour.

Animals↗
PubMed1983

Coexistence of neuropeptides in hydra.

Using a technique for simultaneous visualisation of two antigens in one section, oxytocin-like immunoreactivity has been found to coexist with bombesin-like immunoreactivity in neurons of the basal disk, gastric region and tentacles of hydra. Neurons with oxytocin-like immunoreactivity in peduncle and hypostome, on the other hand, have little or no bombesin-like material. Oxytocin-like immunoreactivity never coexists with FMRFamide-immunoreactivity. The neurons with oxytocin- and FMRFamide-like immunoreactivity, however, are often found to be closely intermingled. The results show that coexistence, as well as non-coexistence, of neuropeptides is a phylogenetically old principle.

Animals↗
PubMed1991

Central neuronal pathways containing FLFQPQRFamide-like (morphine-modulating) peptides in the rat brain.

Octapeptide FLFQPQRFamide (FMRFamide-like peptide; morphine-modulating peptide), isolated from bovine brain, has some opiate analgesia modulating effects. Octapeptide FLFQPQRFamide-like immunoreactivity is found in high concentrations in the posterior pituitary, hypothalamus, pons-medulla, and dorsal spinal cord. Octapeptide FLFQPQRFamide-immunoreactive neurons of the brain are localized in the medial hypothalamus and in the nucleus of the solitary tract. High densities of octapeptide FLFQPQRFamide-immunoreactive nerve terminals are found in the median eminence, lateral parabrachial nucleus, and nucleus of the solitary tract. By using the retrograde tract tracing method combined with immunohistochemistry, we studied the central pathways interconnecting the octapeptide FLFQPQRFamide-immunoreactive structures. The octapeptide FLFQPQRFamide-immunoreactive neurons of the hypothalamus sent projections bilaterally to the nucleus of the solitary tract. The octapeptide FLFQPQRFamide-immunoreactive neurons of the nucleus of the solitary tract projected to the contralateral side of the same nucleus, to the lateral parabrachial nuclei bilaterally, and to the ipsilateral periambigual region. The results give neuroanatomical evidence of interacerebral pathways containing recently identified FLFQPQRFamide-like peptides, which may belong to a larger family of peptides. These neuroanatomical findings support the previous pharmacological studies, suggesting that the mammalian FMRFamide-like peptides may, in addition to modulatory effects on nociceptive mechanisms, participate in the regulation of blood pressure, feeding behaviour and endocrine functions.

Amino Acid Sequence↗
PubMed1987

Effects of synthetic peptides on giant neurons identified in the ganglia of an African giant snail (Achatina fulica Férussac)--II.

Thirteen synthetic biologically-active peptides, which were classified into the peptides proposed as neurotransmitters in mammals and invertebrates and neural venom peptides, were investigated for their effects on the following six identifiable giant neurons of an African giant snail (Achatina fulica Férussac): RAPN (right anterior pallial neuron), INN (intestinal nerve neuron), RPeNLN (right pedal nerve large neuron), LPeNLN (left pedal nerve large neuron), d-LPeLN (dorsal-left pedal large neuron) and d-LPeCN (dorsal-left pedal constantly firing neuron). Oxytocin and proctolin at 10(-4)M excited the RAPN membrane potential, whereas FMRFamide at the same concentration inhibited the same neuron. FMRFamide at 10(-4)M markedly inhibited the d-LPeLN membrane potential, sometimes produced inhibition of RPeNLN and LPeNLN, showed varied effects (excitatory or inhibitory) on INN, and had no effect on d-LPeCN. The other peptides examined had almost no effect on any of the neurons tested.

Animals↗
PubMed1988

Effects of synthetic biologically active peptides on giant neurones identified in the left buccal ganglion of an African giant snail (Achatina fulica Férussac).

1. The effects of synthetic biologically active peptides, including Met-enkephalin, substance P, oxytocin, Arg-vasopressin, proctolin and FMRFamide, on the following four buccal neurones were examined: d-LBAN (dorsal-left buccal anterior neurone), d-LBMN (dorsal-left buccal medial neurone), d-LBCN (dorsal-left buccal central neurone) and d-LBPN (dorsal-left buccal posterior neurone). These peptides were examined at 10(-4) M. 2. Oxytocin excited d-LBAN and slightly excited d-LBCN, while this inhibited d-LBMN. Arg-vasopressin excited slightly d-LBAN and d-LBCN, but this had some times no effect. FMRFamide inhibited d-LBAN, and slightly inhibited d-LBCN. 3. No direct synaptic connection from the two ventral cerebral giant neurones, v-LCDN and v-RCDN, to the four buccal giant neurones was found, though the two cerebral neurones innervate the cerebro-buccal connectives.

Animals↗
PubMed1989

Formation and modulation of chemical connections: evoked acetylcholine release from growth cones and neurites of specific identified neurons.

The ability to release acetylcholine (ACh) from cultured neurons of Helisoma was assessed by micromanipulating ACh-sensitive somata into contact with presynaptic neurons. ACh release was reliably detected from neurites and growth cones of cholinergic neuron B5, but not neuron B19, as early as 3 s after contact with novel target neurons. The rapid onset of transmission correlates with the ability of neuron B5, but not neuron B19, to indiscriminately form chemical connections and may be related to the specificity of synaptogenesis. The neuropeptide FMRFamide reduces ACh release at early chemical connections. The rapid onset of functional transmission and the ability of FMRFamide to modulate chemical transmission at this early chemical connection suggest that neuron B5 acquires its presynaptic apparatus through an intrinsic program independently of target contact.

Acetylcholine↗
PubMed1992

Inhibitors of protein and RNA synthesis block structural changes that accompany long-term heterosynaptic plasticity in Aplysia.

Synaptic connections between the sensory and motor neurons of Aplysia in culture undergo long-term facilitation in response to serotonin (5-HT) and long-term depression in response to FMRFamide. These long-term functional changes are dependent on the synthesis of macromolecules during the period in which the transmitter is applied and are accompanied by structural changes. There is an increase and a decrease, respectively, in the number of sensory neuron varicosities in response to 5-HT and FMRFamide. To determine whether macromolecular synthesis is also required for the structural changes, we examined in parallel the effects of inhibitors of protein (anisomycin) or RNA (actinomycin D) synthesis on the structural and functional changes. We have found that anisomycin and actinomycin D block both the enduring alterations in varicosity number and the long-lasting changes in synaptic potential. These results indicate that macromolecular synthesis is required for expression of the long-lasting structural changes in the sensory cells and that this synthesis is correlated with the long-term functional modulation of sensorimotor synapses.

Animals↗