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PubMed1997

Cholinergic and peptidergic regulation of siphon/mantle function in the zebra mussel, Dreissena polymorpha.

Neurotransmitter regulation of the siphon and adjacent mantle region of bivalves has not previously been examined. In the biofouling bivalve, Dreissena polymorpha, acetylcholine and FMRFamide both elicited contractions of siphon/mantle preparations. Hexamethonium bromide inhibited acetylcholine-elicited contractions but had no effect on FMRFamide-elicited contractions. FMRFamide-like immunoreactivity and chromatographic evidence for acetylcholine were found in central ganglia and the siphon/mantle region. Extracts of siphons, gonads, and gills, separated on Sephadex G-25, also contained macromolecules larger than acetylcholine and FMRFamide that caused siphon/mantle contraction. These results demonstrate regulation of contraction by several potential neurotransmitter agents in a new bivalve preparation, the siphon/mantle.

Acetylcholine↗
PubMed1993

Cytochemical observations on the nervous system of adult Corrigia vitta.

Adult Corrigia vitta (Trematoda: Dicrocoelidea) inhabit the pancreatic duct of the fieldmouse, Apodemus sylvaticus, where, in numbers, they may occlude the duct lumen and prevent the flow of pancreatic secretions. Enzyme histochemical and immunocytochemical techniques, in conjunction with confocal scanning laser microscopy, have been used to examine the localization and distribution of cholinergic, serotoninergic (5-HT, serotonin) and peptidergic components of the nervous system of the adult worm. All three classes of neuronal mediator showed a common pattern of staining, occurring throughout the central and peripheral nervous systems. Of the four peptide immunoreactivities (IR) demonstrated (pancreatic polypeptide (PP), peptide YY (PYY), substance P (SP), FMRFamide), PP-IR was the most predominant, occurring not only within the central ganglia and longitudinal nerve cords, but also in subtegumental plexuses and in fibres associated with the egg-forming apparatus. PYY and FMRFamide IRs were evident throughout the central and peripheral nervous systems; FMRFamide immunostaining, in particular, highlighted innervation of the ootype and immunoreactive cell bodies around the Mehlis' gland. Both SP- and 5-HT-IRs were restricted to the cerebral ganglia, ventral nerve cords and associated cell bodies. The distribution patterns of these peptides and 5-HT within the nervous system of C. vitta suggest they are likely to function as neuronal mediators. PP, PYY and FMRFamide may also serve in regulating egg production.

Animals↗
PubMed1995

The action of serotonin and the nematode neuropeptide KSAYMRFamide on the pharyngeal muscle of the parasitic nematode, Ascaris suum.

The pharyngeal component of the enteric nervous system of the parasitic nematode, Ascaris suum exhibits immunoreactivity for serotonin (5-hydroxytryptamine or 5-HT) and for FMRFamide-like peptides. This paper describes the application of an in vitro pharmacological approach to investigate the functional role of 5-HT and FMRFamide-like peptides. The pharyngeal pumping behaviour of Ascaris suum was monitored using a modified pressure transducer system which measures pharyngeal pressure changes and therefore pumping. The pharynx did not contract spontaneously; however, 5-HT (10-1000 microM) stimulated pumping at a frequency of 0.5 Hz. FMRFamide had no apparent effect on pharyngeal pumping. The native nematode FMRFamide-related peptide (FaRP), KSAYMRFamide inhibited the pumping elicited by 5-HT. The duration of inhibition was dose-dependent (0.1-1000 nM) with a threshold of 0.1 nM. In 4 preparations, the inhibition of the pharyngeal muscle was preceded by an initial excitation and increase in the amplitude of pharyngeal pressure changes. The pharynx is involved in various nematode processes, including feeding, regulation of hydrostatic pressure and excretion. The role of 5-HT and KSAYMRFamide in the pharyngeal function of nematodes is discussed.

Amino Acid Sequence↗
PubMed1988

Long-term heterosynaptic inhibition in Aplysia.

Synaptic transmission between mechanosensory and motor neurons of the gill withdrawal reflex in Aplysia can undergo both short-term and long-term modulation. One form of short-term synaptic depression lasting minutes can be evoked by the peptide Phe-Met-Arg-Phe-amide (FMRFamide), and is mediated by the lipoxygenase pathway of arachidonic acid. We report here using cell culture, that the same monosynaptic sensory-to-motor component of the gill withdrawal reflex can also undergo long-term synaptic depression lasting 24 h after five applications of FMRFamide over a 2-h period. The long-term depression evoked by FMRFamide is transmitter-specific. Dopamine or low-frequency stimulation of sensory neurons, which also produce short-lasting synaptic depression in vivo, failed to evoke a long-term change. As is the case for long-term presynaptic facilitation of this connection with serotonin, the long-term depression, but not the short-term, can be blocked when applications of FMRFamide are given in the presence of anisomycin, a reversible inhibitor of protein synthesis. Thus, heterosynaptic depression parallels heterosynaptic facilitation in having a long-term as well as a short-term form, and in both cases the long-term modulation requires the synthesis of gene products not essential for the short-term changes.

Animals↗
PubMed1986

A neuropeptide precursor expressed in Aplysia neuron L5.

Aplysia abdominal ganglion neuron L5 is immunoreactive with an antiserum generated against the tetrapeptide Phe-Met-Arg-Phe-amide (FMRFamide); however, the specificity of this immune reagent is limited to the sequence Arg-Phe-amide. We isolated cDNA clones homologous to mRNAs specifically expressed in L5 and demonstrated that these clones do not hybridize to a previously characterized gene encoding FMRFamide. The nucleotide sequence of one of these clones, L5-67, does not encode any FMRFamide peptides but does reveal a Gly-Lys-Arg cleavage site following the amino acids Arg-Phe. This data predicts that neuron L5 expresses a peptide ending in Arg-Phe-amide, consistent with the FMRFamide immunoreactivity.

Amino Acid Sequence↗
PubMed1991

Isolation and characterization of authentic Phe-Met-Arg-Phe-NH2 and the novel Phe-Thr-Arg-Phe-NH2 peptide from Nereis diversicolor.

Immunocytochemical studies have shown that peptides like Phe-Met-Arg-Phe-NH2 (FMRFamide) are widely distributed throughout the nervous system of three Nereidae. In Nereis diversicolor we have isolated these peptides from an extract of total worms by affinity chromatography and two steps of reversed-phase high-performance liquid chromatography. The sequences of the purified peptides have been determined by amino acid sequencing and on the basis of their reactivity with an anti-FMRFamide serum specific for the determinant Arg-Phe-NH2. Two primary structures have been established: Phe-Thr-Arg-Phe-NH2 (FTRFamide) and PHe-Met-Arg-Phe-NH2 (FMRFamide). Furthermore a methionine sulfoxide derivative of the FMRFamide has been identified. We have synthesized the FTRFamide peptide and in all cases, the native peptides were indistinguishable from the synthetic counterparts. The structure of the two native peptides and of the methionyl sulfoxide derivate have been confirmed by fast-atom-bombardment and tandem mass spectrometry.

Amino Acid Sequence↗
PubMed1998

Single-channel currents of a peptide-gated sodium channel expressed in Xenopus oocytes.

1. Single-channel recordings were made from outside-out membrane patches of Xenopus oocytes injected with the cDNA clone FaNaCh, which encodes a peptide-gated Na+ channel from Helix aspersa. 2. The natural peptides FMRFamide and FLRFamide only activated unitary currents in oocytes injected with FaNaCh; the EC50 values were 1.8 and 11.7 microM, respectively. 3. The slope conductance of the channel was 9.2 pS for both peptides. 4. With FMRFamide, the open probability (Po) of the channel was 0.06 at 0.3 microM and 0.76 at 30 microM, whereas for FLRFamide the open probability increased from 0.04 at 1.8 microM to 0.49 at 50 microM. The Hill coefficient was greater than 1 for both peptides. 5. High concentrations of each peptide evoked very fast flickering between open and closed states which led to decreased unitary current amplitude. 6. At low doses, brief single openings and bursts of longer openings occurred. With higher doses, the occurrence of the brief openings declined and the number of longer openings increased; the duration of the longer openings was shorter with FLRFamide than with FMRFamide. 7. For each peptide, frequency distribution histograms of open events were best fitted by the sum of two exponential components, suggesting the existence of two open states of the channel. Closed events were fitted by the sum of three components, suggesting the existence of three closed states. 8. The data were analysed according to a five-state model in which the brief openings correspond to a single liganded open form of the channel and the longer openings to a doubly liganded open form. According to this interpretation, the greater whole-cell response observed with FMRFamide than with FLRFamide results mostly from a slower closing rate constant for the longer (doubly liganded) channel openings.

Animals↗
PubMed1990

Pharmacology of the myogenic heart of the pond snail Lymnaea stagnalis.

1. We have used pharmacologic, immunologic, and biochemical techniques to examine the role of neurochemicals in modulating the myogenic heart of the snail, Lymnaea. 2. 5-HT [high-pressure liquid chromatography (HPLC) and immunocytochemistry], dopamine (HPLC), FMRFamide-related peptides (radioimmunoassay and immunocytochemistry) and substance P-related peptides (immunocytochemistry) were shown to be localized within heart tissue. 3. The pharmacologic actions of these substances on the auricle from an isolated heart preparation were examined together with other putative modulators, acetylcholine (ACh), small cardioactive peptides A and B (SCPA and SCPB), [Arg]8vasotocin (AVT), and Lymnaea native FMRFamide-related peptides [Phe-Met-Arg-Phe-NH2 (FMRFamide), Ser-Asp-Pro-Phe-Leu-Arg-Phe-NH2 (SDPFLRFamide) and Gly-Asp-Pro-Phe-Leu-Arg-Phe-NH2 (GDPFLRFamide)]. 4. The response to each substance could be distinguished by different effect on beat rate, amplitude, and diastolic tonus, as well as by the duration of responses to standard 1-min applications. ACh was inhibitory at low concentrations (threshold less than 10(-10) M) but excitatory at high concentrations (10(-6) M). AVT was alone in producing no dose-dependent response. At high concentrations (10(-4) M), AVT caused a massive tonic contraction and cessation of auricle beat. All other substances examined were excitatory. 5. Antagonists to 5-HT (cinanserin), dopamine (ergonovine), and ACh (alpha-bungarotoxin) were identified. 6. ACh, 5-HT, dopamine, and FMRFamide-related peptides all acted on the auricle at low concentrations, and the rapid onset and short duration of their excitatory effects (ACh inhibitory at low concentrations) suggested that they may have roles as neurotransmitters. SCPA and SCPB were also potent (threshold less than 10(-10) M) but produced long-duration responses suggesting a modulatory or hormonal role.

Animals↗
PubMed1999

Modulation of radula opener muscles in Aplysia.

We observed fibers immunoreactive (IR) to serotonin (5-HT), the myomodulins (MMs), and FMRFamide on the I7-I10 complex in the marine mollusk Aplysia californica. The I7-I10 muscle complex, which produces radula opening, is innervated primarily by one motor neuron, B48. B48 is MM-IR and synthesizes authentic MM(A). When B48 is stimulated in a physiological manner, cAMP levels are increased in opener muscles. cAMP increases also are seen when the MMs are applied to opener muscles but are not seen with application of the B48 primary neurotransmitter acetylcholine (ACh). Possible physiological sources of 5-HT and FMRFamide are discussed. When modulators are applied to resting opener muscles, changes in membrane potential are observed. Specifically, 5-HT, MM(B), and low concentrations of MM(A) all depolarize muscle fibers. This depolarization is generally not sufficient to elicit myogenic activity in the absence of neural activity under "rest" conditions. However, if opener muscles are stretched beyond rest length, stretch- and modulator-induced depolarizations can summate and elicit contractions. This only occurs, however, if "depolarizing" modulators are applied alone. Thus other modulators (i.e., FMRFamide and high concentrations of MM(A)) hyperpolarize opener muscle fibers and can prevent depolarizing modulators from eliciting myogenic activity. All modulators tested affected parameters of motor neuron-elicited contractions of opener muscles. MM(B) and 5-HT increased contraction size over the range of concentrations tested, whereas MM(A) potentiated contractions when it was applied at lower concentrations but decreased contraction size at higher concentrations. FMRFamide decreased contraction size at all concentrations and did not affect relaxation rate. Additionally, the MMs and 5-HT increased muscle relaxation rate, decreased contraction latency, and decreased the rate at which tension was developed during motor neuron-elicited muscle contractions. Thus these modulators dramatically affect the ability of opener muscles to follow activity in the opener motor neuron B48. The possible physiological significance of these findings is discussed.

Animals↗
PubMed1995

An endogenous peptide modulates the activity of a sensory neurone in the leech Hirudo medicinalis.

Sensory and neurosecretory innervation of each leech excretory complex, a nephridium and its bladder, is accomplished by a single neurone, the nephridial nerve cell (NNC). The NNC monitors the extracellular Cl- concentration, which ranges between 20 and 100 mmol l-1 depending on the physiological state. The NNC contains FMRFamide in its soma and sensory terminals in the nephridium. Bath or focal application of FMRFamide leads to hyperpolarization and decreases the rate of firing of the NNC, suggesting autoregulation of peptide release. Experiments under single-electrode current-clamp and voltage-clamp show that FMRFamide turns off the receptor-specific Cl- current of the NNC, indicating that FMRFamide also modulates the receptor gain.

Animals↗
PubMed2005

Immunocytochemical identification of neuroactive substances in the antennal lobe of the male silkworm moth Bombyx mori.

As a first step towards understanding the functional role of neuroactive substances in the first olfactory center of the male silkworm moth Bombyx mori, we carried out an immunocytochemical identification of antennal lobe neurons. Antibodies against gamma-aminobutyric acid (GABA), FMRFamide, serotonin, tyramine and histamine were applied to detect their existence in the antennal lobe. In the present immunocytochemical study, we clarified four antenno-cerebral tracts from their origin and projection pathways to the protocerebrum, and revealed the following immunoreactive cellular organization in the antennal lobe. 1) Local interneurons with cell bodies in the lateral cell cluster showed GABA, FMRFamide and tyramine immunoreactivity. 2) Projection neurons passing through the middle antenno-cerebral tract with cell bodies in the lateral cell cluster showed GABA and FMRFamide immunoreactivity. Projection neurons passing through the outer antenno-cerebral tract with cell bodies in the lateral cell cluster showed FMRFamide immunoreactivity. 3) Centrifugal neurons passing through the inner antenno-cerebral tract b with cell bodies located outside the antennal lobe showed serotonin and tyramine immunoreactivity. Our results revealed basic distribution patterns of neuroactive substances in the antennal lobe and indicated that each projection pathway from the antennal lobe to the protocerebrum contains specific combination of neuroactive substances.

Animals↗
PubMed2001

Physiological and pharmacological characteristics of quisqualic acid-induced K(+)-current response in the ganglion cells of Aplysia.

The extracellular application of either quisqualic acid (QA) or Phe-Met-Arg-Phe-NH2 (FMRFamide) induces an outward current in identified neurons of Aplysia ganglion under voltage clamp. The time course of the QA-induced response is significantly slower than that induced by FMRFamide. The reversal potential for both responses was -92 mV and was shifted 17 mV in a positive direction for a twofold increase in the extracellular K(+) concentration. The QA-induced response was markedly depressed in the presence of Ba(2+), a blocker of inward rectifier K(+)-channel, whereas TEA, a Ca(2+)-activated K(+)-channel (BK(Ca)) blocker, or 4-AP, a transient K(+) (A)-channel blocker, had no effect on the response. The QA-induced K(+)-current was significantly suppressed by CNQX and GYKI52466, antagonists of non-NMDA receptors. However, the application of either kainate or AMPA, agonists for non-NMDA receptors, produced no type of response in the same neurons. The QA-induced K(+)-current response was not depressed at all by an intracellular injection of either guanosine 5'-O-(2-thiodiphosphate) (GDP-betaS) or guanosine 5'-O-(3-thiotriphosphate) (GTP-gammaS), but the FMRFamide-induced response was markedly blocked by both GDP-betaS and GTP-gammaS in the same cell. Furthermore, the QA- and FMRFamide-induced K(+)-current responses were both decreased markedly when the temperature was lowered to 15 degrees C, from 23 degrees C. These results suggested that the QA-induced K(+)-current response is produced by an activation of a novel type of QA-receptor and that this response is not produced by an activation of the G protein.

Action Potentials↗
PubMed1995

Changes in expression and distribution of Aplysia cell adhesion molecules can influence synapse formation and elimination in vitro.

5-HT or FMRFamide evoke long-lasting changes in the efficacy of sensorimotor (SN-L7) synapses of Aplysia, structural alterations of the presynaptic sensory cell, and cell-specific downregulation in the distribution of the adhesion molecule apCAM. We examined how the cell-specific changes in apCAM might contribute to the formation of new presynaptic varicosities by 5-HT or the elimination of existing presynaptic varicosities by FMRFamide. We report that the formation of new sensory varicosities is directed by the presence of preexisting zones on the motor axon that are enriched for apCAM. Moreover, there was a further enrichment of apCAM levels at existing sensory varicosities contacting the motor axon beginning at 1 hr and lasting 24 hr after treatment with 5-HT. As was found for synapse formation during the early stages of cell-cell interaction, incubation with anti-apCAM mAb blocked the 5-HT-induced long-term changes in synaptic efficacy and the accompanying changes in sensory neuron structure. Long-term synaptic depression with FMRFamide was accompanied by an overall decline of apCAM levels. Treatment with FMRFamide evoked an even greater decline in apCAM levels at sites of sensory varicosities that preceded the structural changes and persisted especially at sites where sensory varicosities are eliminated. These results suggest that neurotransmitters evoke both cell- and site-specific changes in the levels of adhesion molecules that can influence either the formation or the elimination of presynaptic varicosities that accompany long-term heterosynaptic modulation of a behaviorally relevant synaptic connection.

Animals↗
PubMed1994

Neuropeptides myomodulin, small cardioactive peptide, and buccalin in the central nervous system of Lymnaea stagnalis: purification, immunoreactivity, and artifacts.

The neuropeptides myomodulin, small cardioactive peptide (SCP), and buccalin are widely distributed in the phylum Mollusca and have important physiological functions. Here, we describe the detailed distribution of each class of peptide in the central nervous system (CNS) of the snail Lymnaea stagnalis by the use of immunocytochemical techniques combined with dye-marking of electrophysiologically identified neurons. We report the isolation and structural characterization of a Lymnaea myomodulin, PMSMLRLamide, identical to myomodulin A of Aplysia californica. Myomodulin immunoreactivity was localized in all 11 ganglia, in their connectives, and in peripheral nerves. In many cases, myomodulin immunoreactivity appeared localized in neuronal clusters expressing FMRFamide-like peptides, but also in a large number of additional neurons. Double-labelling experiments demonstrated myomodulin immunoreactivity in the visceral white interneuron, involved in regulation of cardiorespiration. SCP-like immunoreactivity also appeared in all ganglia, and double-labelling experiments revealed that in many locations it was specifically associated with clusters expressing distinct exons of the FMRFamide gene that are differentially expressed in the CNS. Characterization of the two types of SCP-antisera used in this study, however, suggested that they cross-reacted with both FMRFamide and N-terminally extended FMRFamide-like peptides. Selective preadsorption with these cross-reacting peptides resulted in elimination of the widespread staining and retention of bona fide SCP immunoreactivity in the buccal and pedal ganglia only. Buccalin immunoreactivity was limited to the buccal and pedal ganglia. It did not coincide with the distribution of either myomodulin or SCP. Most immunoreactive clusters were found in the pedal ganglia.

Amino Acid Sequence↗
PubMed1991

Cytochemical demonstration of cholinergic, serotoninergic and peptidergic nerve elements in Gorgoderina vitelliloba (Trematoda: Digenea).

Standard enzyme cytochemical and indirect immunocytochemical techniques have been used in conjunction with light and confocal scanning laser microscopy (CSLM) to visualize cholinergic, serotoninergic and peptidergic nerve elements in whole-mount preparations of the amphibian urinary-bladder fluke, Gorgoderina vitelliloba. Cholinesterase (ChE) activity was localized in paired anterior ganglia, a connecting dorsal commissure and in the origins of the ventral nerve cords. Cholinergic ganglia were also evident in shelled embryos in the uterus. Serotonin-immunoreactivity (IR) was more extensive than ChE activity and was identified in both the central and peripheral nervous systems. Serotoninergic nerve fibres were associated with the somatic musculature and female reproductive ducts. Antisera to nine mammalian peptides and one invertebrate (FMRFamide) peptide have been used to investigate the peptidergic nervous system in the parasite. Immunoreactivity was obtained to five peptides, namely pancreatic polypeptide (PP), peptide YY (PYY), neuropeptide Y (NPY), substance P (SP) and FMRFamide. Peptidergic nerve fibres were found to be more abundant than demonstrable cholinergic or serotoninergic nerve fibres. NPY-IR was identified only in the main components of the central nervous system. However, PP- and PYY-IR occurred in the anterior ganglia, dorsal commissure, main nerve cords and in numerous small varicose fibres that ramified throughout the worm. Additionally, PP-immunoreactive nerve fibres were found to innervate the musculature of the female reproductive tracts. Six sites of IR were found in the acetabulum, using antisera directed towards the C-terminal end of PP and PYY, and these matched with the distribution of six non-ciliated rosette-like papillae observed by scanning electron microscopy. SP- and FMRFamide-IR were identified in the CNS, and FMRFamide-immunopositive nerve fibres were also evident in association with the gonopore cirrus region and with the terminal excretory pore. Results are discussed with respect to possible roles for each of the neurochemical types.

Animals↗
PubMed1985

Peptidergic modulation of patterned motor activity in identified neurons of Helisoma.

The neuroactive peptides SCP(B) (small cardioactive peptide B) and FMRFamide (Phe-Met-Arg-Phe-NH(2)), both originally isolated from molluscs, have potent modulatory effects upon the production of patterned motor activity in identified neurons (e.g., B5 and B19) in the buccal ganglia of the snail Helisoma. Such patterned motor activity has previously been shown to underlie feeding behavior. Micromolar concentrations of SCP(B) initiate patterned motor activity in quiescent ganglia and increase the rate of activity in ganglia that are spontaneously active. Micromolar concentrations of FMRFamide inhibit patterned motor activity in Helisoma buccal ganglia, and 10 muM FMRFamide completely suppresses such activity. In addition, there are both anti-SCP(B)-and anti-FMRFamide-immunoreactive neurons in Helisoma buccal ganglia. Our results suggest that peptides may play a prominent role in the regulation of feeding behavior in Helisoma.

Journal Article↗
PubMed1994

THE MODULATORY EFFECT OF SCHISTOFLRFamide ON HEART AND SKELETAL MUSCLE IN THE LOCUST SCHISTOCERCA GREGARIA

SchistoFLRFamide (PDVDHVFLRFamide) is one of the endogenous FMRFamide-like neuropeptides found in the nervous system of the locust Schistocerca gregaria (Robb et al. 1989; Robb and Evans, 1990). FMRFamide-like neuropeptides modulate the actions of a wide variety of both skeletal and visceral muscles in insects (Evans and Myers, 1986a; Schoofs et al. 1993b) and have been suggested to act both as circulatory hormones and as locally released neurotransmitters (see discussion in Robb and Evans, 1990). However, the behavioural context(s) in which such neuropeptides are released is at present unclear, although recent evidence suggests they may have a role in feeding behaviour (Elia et al. 1993). SchistoFLRFamide belongs to one of the subclasses of FMRFamide-like neuropeptides found in insects, which also includes leucomyosuppressin (pQDVDHVFLRFamide; Holman et al. 1986), ManducaFLRFamide (pQDVVHSFLRFamide; Kingan et al. 1990) and TDVDHVFLRFamide found in both Drosophila melanogaster (Nichols, 1992) and Neobellieria bullata (Fonagy et al. 1992). The sequence of SchistoFLRFamide has also been found in Locusta migratoria (Schoofs et al. 1993a). SchistoFLRFamide was originally isolated from the nervous system of Schistocerca gregaria using a combination of radioimmunoassay, HPLC and bioassay (Robb et al. 1989; Robb and Evans, 1990). Preliminary data indicate that it inhibits spontaneous contractions of the locust heart and has a complex dose-dependent effect upon contractions induced in the extensor tibiae muscle by stimulation of the slow excitatory motoneurone (Robb et al. 1989). In addition, SchistoFLRFamide has recently been shown to decrease the amplitude and frequency of myogenic contractions and to reduce basal tension in locust oviduct muscle (Peeff et al. 1993). The present paper provides a more detailed account of the modulatory effect of SchistoFLRFamide on heart and skeletal muscle in the locust Schistocerca gregaria. The effects of the synthetic peptide were measured on the semi-isolated locust heart (Cuthbert and Evans, 1989). The results are expressed as the percentage change in the amplitude of the heartbeat and its frequency with respect to measurements obtained immediately before the application of the peptide. Measurements of heart rate and contraction amplitude were averaged over a 1 min period, starting (a) 1 min before the beginning of the peptide pulse, (b) 1 min after the start of the peptide pulse, (c) 4 min after the start of the peptide pulse and (d) 1 min after the end of the peptide pulse. The bioactivity of synthetic SchistoFLRFamide was also assayed on another well-defined FMRFamide bioassay preparation from the locust. The effects were measured on the twitch tension evoked in the extensor tibiae muscle of the hindleg of the locust by stimulating the slow excitatory motoneurone to this muscle at 1 Hz (Evans and Myers, 1986b). The results are expressed as the maximal effects on the twitch amplitude.

Journal Article↗
PubMed1996

Neuroanatomy and immunocytochemistry of the median neuroendocrine cells of the subesophageal ganglion of the tobacco hawkmoth, Manduca sexta: immunoreactivities to PBAN and other neuropeptides.

The median neuroendocrine cells of the subesophageal ganglion, important components of the neuroendocrine system of the tobacco hawkmoth, Manduca sexta, have not been well investigated. Therefore, we studied the anatomy of these cells by axonal backfills and characterized their peptide immunoreactivities. Both larvae and adults were examined, and developmental changes in these neuroendocrine cells were followed. Processes of the median neuroendocrine cells project to terminations in the corpora cardiaca via the third and the ventral nerves of this neurohemal organ, but the ventral nerve of the corpus cardiacum is the principal neurohemal surface for this system. Cobalt backfills of the third cardiacal nerves revealed lateral cells in the maxillary neuromere and a ventro-median pair in the labial neuromere. Backfills of the ventral cardiacal nerves revealed two ventro-median pairs of cells in the mandibular neuromere and two ventro-median triplets in the maxillary neuromere. The efferent projections of these cells are contralateral. The anatomy of the system is basically the same in larvae and adults. The three sets of median neuroendocrine cells are PBAN- and FMRFamide-immunoreactive, but only the mandibular and maxillary cells are proctolin-immunoreactive. During metamorphosis, the mandibular and maxillary cells also acquire CCK-like immunoreactivity and the labial cells become SCP- and sulfakinin-immunoreactive. Characteristics of FMRFamide-like immunostaining suggest that the median neuroendocrine cells may contain one or more of the FLRFamides that have been identified in M. sexta. The mandibular and maxillary neuroendocrine cells appear to produce the same set of hormones, and a somewhat different set of hormones is produced by the labial neuroendocrine cells. Two pairs of interneurons immunologically related to the neurosecretory cells are associated with the median maxillary neuroendocrine cells. These cells are PBAN-, FMRFamide-, SCP-, and sulfakinin-immunoreactive and project to arborizations in the brain and all ventral ganglia. These interneurons appear to have extensive modulatory functions in the CNS.

Animals↗