Hyperneural Muscle Research Articles

The pregenital abdomen of a mantid and a cockroach: Musculature and nerve topography, with comparative remarks on other neoptera (Insecta: Dictyoptera)

Musculature and nerve topography of the middle (“typical”) abdominal segments III–VI are described for male Periplaneta (Blattaria) and Sphodromantis (Mantodea). Many additions and differences to earlier contributions are included. Segmental and individual variation are considered. Differences between Periplaneta and Sphodromantis are discussed. Characters are polarised by outgroup comparison with other Neoptera and made available for phylogenetic analysis in Dictyoptera. Some proposals for muscle and nerve terminologies are given. The musculature is very similar in the two species, but Sphodromantis lacks a hyperneural muscle. Nerve topography is also largely similar, but there are striking differences in the anastomoses between the main nerves and in the spatial relations between certain nerves and muscles. A paramedian nerve was found in Periplaneta but not in Sphodromantis. In both species, segmental and individual variation are sparse in the musculature but rather extensive in the nervous system. Apomorphies of Periplaneta are the degeneration of the anterior tergo-coxosternal muscles (still well-developed in nymphs), the loss of transverse striation in the median external ventral muscles (still present in nymphs), and the presence of an anastomosis between the two major branches of the ventral nerve. Apomorphies of Sphodromantis are the loss of the hyperneural muscle, the loss of the anastomosis between ventral and transverse nerve, the presence of an anastomosis between dorsal and ventral nerve, and possibly the loss of the paramedian nerve. Some of the discussed characters could be useful in the phylogenetic analysis of the Dictyoptera, also regarding the position of the Isoptera.

The potential value of the mid-abdominal musculature and nervous system in the reconstruction of interordinal relationships in Lower Neoptera

The mid-abdominal musculature and its innervation are compared for several lower neopteran “orders”; data on Embioptera and Mantophasmatodea are presented for the fi rst time. For the sclerotisations, the musculature, and the nervous system of the mid-abdomen general descriptions are given, and general aspects of homologisation in these elements are explained; for the lateral muscles the distinction of three groups innervated by the T-, B-, or C-nerves is confi rmed. Differences in the musculature and nervous system of the lower neopteran lineages are discussed and evaluated with regard to their phylogenetic implications. Conditions in Ephemeroptera, Megaloptera, and Zygentoma are partly included in the discussion. Several characters were found to be informative on interordinal relationships. Plecoptera have features probably plesiomorphic at the neopteran level: the origin of nerve A in front of the ganglion and the innervation of intrasegmental lateral muscles by nerve A; this may support the monophyly of a taxon comprising all other Neoptera. The hyperneural muscle found in many Dictyoptera also appears as a uniquely plesiomorphic structure (at the pterygotan level). The co-occurrence of two specifi c lateral muscles supplied by nerve B as well as certain subdivisions in the lateral muscles may support a clade Phasmatodea + Embioptera. We also point to character systems that appear informative on the internal phylogeny of order-level taxa, such as the relationships between nerves T and M in Plecoptera, the ventral musculature in Ensifera, the dorsal musculature in Dermaptera, and details of the hyperneural muscle in Dictyoptera. Besides the very low number of taxa studied so far, major problems still persistent in the use of mid-abdominal characters for phylogenetic work are (1) the insuffi cient knowledge on topographic homologies for the lateral cuticular areas of the mid-abdomen; (2) lacking knowledge on the neuronal structural level of the mid-abdominal nervous system; (3) diffi culties in the homologisation of muscles and nerves between Pterygota and the apterygote Archaeognatha and Zygentoma, which are partly due to the presence of a system of non-cuticular tendons in the latter and limit outgroup comparison for Pterygota.

Identical cellular distribution of all abundant neuropeptides in the major abdominal neurohemal system of an insect (Periplaneta americana).

The median neurosecretory cells in abdominal ganglia of insects synthesize a number of putative hormones, which are abundant in the abdominal perisympathetic organs (PSOs). The peptide inventory of these prominent neurohemal release sites is best investigated in the American cockroach and strongly differs from that of head/thoracic neurohemal organs. In this study, we found a complete colocalization of all abundant neuropeptides in this hormonal system, including periviscerokinin-1 and -2, pyrokinin-5, YLSamide, VEAacid, and SKNacid. The first immunoreactive cells were detected on day 18 of embryonic development and already contained the complete set of peptides. By using antisera against the above-mentioned peptides, the development of this neurohormonal system could be studied and is described in detail. Subsequent electron microscopic immunogold stainings in PSO preparations revealed the costorage of PSO peptides in a single vesicle species. Surprisingly, all these peptides were found in axons containing clear vesicles, whereas all axons with dense core vesicles were totally devoid of immunoreactivity. Unlike the axons with dense core vesicles, immunostained axons ramify in the center of the PSO but exhibit only rare morphological signs of exocytosis. Instead, putative release sites of the clear vesicle-containing axons were detected peripherally to the PSOs, namely, on the hyperneural muscle.

The Drosophila hugin gene codes for myostimulatory and ecdysis-modifying neuropeptides

In a genomic screen we isolated the Drosophila gene hugin ( hug, cytology 87C1-2) by cross-hybridisation to a human glial cell line-derived neurotrophic factor cDNA. Upon cDNA sequence analysis and in vitro expression assays, the hugin gene was found to encode a signal peptide containing proprotein that was further processed in Schneider-2 cells into peptides similar to known neuropeptides. Two of the peptides were similar to FXPRL-amides (pyrokinins) and to the ecdysis-triggering hormone, respectively. The former displayed myostimulatory activity in a bioassay on the cockroach hyperneural muscle preparation, as well as in the Drosophila heart muscle assay. Hugin is expressed during the later half of embryogenesis and during larval stages in a subgroup of neurosecretory cells of the suboesophageal ganglion. Ubiquitous ectopic hugin expression resulted in larval death predominantly at or shortly after ecdysis from second to third instar, suggesting that at least one of the posttranslational cleavage products affects molting of the larva by interfering with the regulation of ecdysis.

Periviscerokinins in Cockroaches: Release, Localization, and Taxon-Specific Action on the Hyperneural Muscle

The periviscerokinins of Periplaneta americana (Pea-PVKs) were the first neuropeptides directly isolated from perisympathetic organs (PSOs), neurohemal swellings of the transverse and median nerves of insects. It has been demonstrated that Pea-PVK-1 release can be induced from the abdominal PSOs of P. americana by in vitro depolarization. A myotropic effect of Pea-PVK-1 on the hyperneural muscle is restricted to blattid cockroaches, whereas proctolin induces contractions of this muscle in all cockroach species investigated. The location and morphology of Pea-PVK-1-like immunoreactive neurons in species of different cockroach taxa are very similar to those previously described for P. americana. Pea-PVK-1-like immunoreactivity is restricted to cells of the abdominal ganglia which constitute a neurohemal system and project via the median nerve to the abdominal PSOs. Despite interspecific differences in the topography of the transverse nerves of the terminal ganglion, Pea-PVK-1-like immunoreactive fibers always innervate transversal nerves VII and VIII of the terminal ganglion. The results suggest that PVKs act as neurohormones throughout the cockroaches, although they may have different effect(s) depending on the species.

Efficacy of native FXPRLamides (pyrokinins) and synthetic analogs on visceral muscles of the American cockroach

Six pyrokinins, members of a widely distributed neuropeptide family in insects (FXPRLamides), have been identified from the American cockroach. Five of these peptides, Pea-PK-1–5, were tested in different myotropic bioassays, including hyperneural muscle, hindgut, foregut and oviduct. Among these muscles, the hyperneural muscle exhibited the highest sensitivity to pyrokinin applications. The efficacy of the different pyrokinins differed dramatically. No muscle specific effectiveness was obtained; the ranking order in all muscle assays was as follows: PK-1>PK-4>PK-3>PK-2>PK-5. Testing of synthetic analogs revealed the importance of the amino acid at the variable -4 position of the C-terminus. PK-5, the only one of the five tested peptides which is stored in abdominal perisympathetic organs, has probably no myotropic function at all. This is further evidence that these neurohemal release sites are not necessary to compensate the open circulatory system of insects but have rather specific functions which are totally unknown as yet.

Peptide-induced Ca(2+) movements in a tonic insect muscle: effects of proctolin and periviscerokinin-2.

Although most of the characterized insect neuropeptides have been detected by their actions on muscle contractions, not much is known about the mechanisms underlying excitation-contraction coupling. Thus we initiated a pharmacological study on the myotropic action of the peptides periviscerokinin-2 (PVK-2) and proctolin on the hyperneural muscle of the cockroach Periplaneta americana. Both peptides required extracellular Ca(2+) to induce muscle contraction, and a blockage of sarcolemmal Ca(2+) channels by Mn(2+) or La(3+) inhibited myotropic effects. The peptides were able to induce contractions in dependence on the extracellular Ca(2+) concentration in muscles depolarized with high K(+) saline. A reduction of extracellular Na(+), K(+), or Cl(-) did not effect peptide action. Nifedipine, an L-type Ca(2+)-channel blocker, partially blocked the response to both peptides but to a much lesser extent than contractions evoked by elevated K(+). Using calcium imaging with fluo-3, we show that proctolin induces an increase of the intracellular Ca(2+) concentration. In calcium-free saline, no increase of the intracellular Ca(2+) concentration could be detected. The inhibiting effect of ryanodine, thapsigargin, and TMB-8 on peptide-induced contractions suggests that Ca(2+) release from the sarcoplasmic reticulum plays a major role during peptide-induced contractions. Preliminary experiments suggest that the peptides do not employ cyclic nucleotides as second messengers, but may activate protein kinase C. Our results indicate that the peptides induce Ca(2+) influx by an activation or modulation of dihydropyridine-sensitive and voltage-independent sarcolemmal Ca(2+) channels. Ca(2+)-induced Ca(2+) release from intracellular stores, but not inositol trisphosphate-induced Ca(2+) release, seems to account for most of the observed increase in intracellular Ca(2+). Additionally, both peptides were able to potentiate glutamate-induced contractions at threshold concentrations.

Differential distribution of pyrokinin-isoforms in cerebral and abdominal neurohemal organs of the American cockroach

Different pyrokinin isoforms were identified from major neurohemal organs of the American cockroach. During their isolation they were recognized by bioassay using a hyperneural muscle preparation that is sensitive to pyrokinins. All structures were elucidated by sequence analysis and mass spectrometry. The primary structures of the novel peptides isolated from the retrocerebral complex are LVPFRPRL-NH 2 (designated Pea-PK-3) and DHLPHDVYSPRL-NH 2 (designated Pea-PK-4). A pyrokinin, labeled Pea-PK-5, was isolated from abdominal perisympathetic organs. Structural analysis of this peptide yielded the sequence GGGGSGETSGMWFGPRL-NH 2. The threshold concentrations of the identified pyrokinins for an eliciting effect on contractions of the hyperneural muscle preparations differed dramatically. This indicates that the different distribution of pyrokinin-isoform observed in neurohemal organs may be associated with different functions. This is the first report of a differential distribution of peptide-isoforms in the neurohemal organs of insects.

Periviscerokinin-like immunoreactivity in the nervous system of the American cockroach.

A highly specific polyclonal antiserum has been raised against periviscerokinin, the first neuropeptide isolated from the perisympathetic organs of insects (Predel et al. 1995). In this study, two different neuronal systems with periviscerokinin-like immunoreactivity were distinguished in the central nervous system of the American cockroach: (1) An intrinsic neuronal network, restricted to the head-thoracic region, was formed by intersegmental projecting neurons of the brain, suboesophageal ganglion and metathoracic ganglion. In addition, groups of local interneurons occurred in the proto- and tritocerebrum. (2) A typical neurohormonal system was stained exclusively in the abdomen; it was represented by abdominal perisympathetic organs which were supplied by three cell clusters located in each unfused abdominal ganglion. As revealed by nickel backfills, most neurons with axons entering the perisympathetic organs contained a periviscerokinin-like peptide. Immunoreactive fibres left the perisympathetic organs peripherally, innervated the hyperneural muscle and ran via the link nerves/segmental nerves to the heart and segmental vessels. All visceral muscles innervated by periviscerokinin-immunoreactive fibres were shown to be sensitive to periviscerokinin, whereas the hindgut gave no specific response to this peptide.

Isolation of Periviscerokinin-2 from the Abdominal Perisympathetic Organs of the American Cockroach, Periplaneta americana

Using the isolated hyperneural muscle as bioassay, a novel myotropin was isolated from the abdominal perisympathetic organs of Periplaneta americana. This is the second neuropeptide identified from insect perisympathetic organs. Peptide sequence analysis and mass spectrometry yielded the following structure: Gly-Ser-Ser-Ser-Gly-Leu-Ile-Ser-Met-Pro-Arg-Val-NH 2. This peptide, named periviscerokinin-2, was confirmed to be amidated by chemical synthesis, bioassay, and comparison of retention times between native and synthetic peptides. A highly specific antiserum was used to determine sites of synthesis in the abdominal ganglia. Besides periviscerokinin-1, periviscerokinin-2 is the only putative myotropic neurohormone from the abdominal perisympathetic organs that is effective in the nanomolar range. This confirms the hypothesis that the neurohormonal system of the ventral nerve cord is remarkably different from that of the brain.

Isolation and Structural Elucidation of Two Pyrokinins From the Retrocerebral Complex of the American Cockroach

Predel, R., R. Kellner, R. Kaufmann, H. Penzlin and G. GÄDe. Isolation and structural elucidation of two pyrokinins from the retrocerebral complex of the American cockroach. Peptides 18(4) 473–478, 1997.— By monitoring the contractile activity of the hyperneural muscle of the American cockroach in vitro two peptides were isolated from the retrocerebral complex of the American cockroach. Three purification steps using reversed-phase high performance liquid chromatography on C-18 columns containing trifluoroacetic acid or heptafluorobutyric acid as organic modifiers were sufficient to achieve homogenous peptide preparations. The structures of both peptides were elucidated by a combination of Edman degradation and mass spectrometry which yielded the following structures: His-Thr-Ala-Gly Phe-Ile-Pro-Arg-Leu-NH 2 (Pea-PK-1) and Ser-Pro-Pro-Phe-Ala-Pro-Arg-Leu-NH 2 (Pea-PK-2). The C-terminal sequence Phe-X-Pro-Arg-Leu-NH 2 characterized the peptides as members of the insect pyrokinin family. The synthetic peptides were shown to have the same retention times as the natural peptides. The occurrence of both peptides in the retrocerebral complex suggests a physiological role as neurohormones. The effects of the synthetic pyrokinins were clearly distinguishable in their actions on the hyperneural muscle. Regarding the threshold concentrations, Pea-PK-2 was only 0.3% as active as Pea-PK-1.

Periviscerokinin (Pea-PVK): A novel myotropic neuropeptide from the perisympathetic organs of the American cockroach

A myotropic neuropeptide was isolated from extracts of 1000 abdominal perisympathetic organs of males of the cockroach, Periplaneta americana. This peptide, termed periviscerokinin, has excitatory actions on the hyperneural muscle of Periplaneta americana. After peptide sequence analysis and mass spectrometry, the structure of this peptide was confirmed by chemical synthesis and bioassay to be Gly-Ala-Ser-Gly-Leu-Ile-Pro-Val-Met-Arg-Asn-NH2. This sequence is different from the other known myotropic peptides in insects. The threshold concentration for stimulatory effects of the synthetic peptide on the isolated hyperneural muscle was about 10(-9) M, suggesting a physiological role as a neurohormone.

Antagonistic control of the hyperneural muscle in Periplaneta americana (L.) (Insecta, Blattaria)

The hyperneural muscle extends longitudinally in the abdomen dorsally to the nerve cord. It is innervated (1) by the six abdominal transverse nerves branching in pairs from the median nerves, (2) by the 7th transverse nerves arising from the terminal ganglion and (3) by the ramus hyperneuromuscularis of the nerve VIII A 1 of the terminal ganglion. The results of this study document that the hyperneural muscle is under antagonistic neuronal control comparable to the sympathetic and parasympathetic innervation of internal organs in vertebrates. Stimulation via the transverse nerve 2, transverse nerve 7 or nerve VIII results in a sustained contraction of the hyperneural muscle. In contrast, stimulation via the transverse nerves 3, 4, 5, or 6 induces a drastic relaxation of the muscle. The only factors known initiating a contraction of the muscle are neuropeptides, namely proctolin and corazonin. None of the “classic” transmitters tested causes a contraction of the muscle under isometric conditions. Acetycholine, taurine, histamine and glycine in concentration of 10 −5 mol/l had no effect at all. GABA, glutamate, 5-HT, octopamine, dopamine and noradrenaline all have a relaxing effect on the muscle. The sequence of decreasing effectiveness was: OA > NA > 5-HT > DA = Glu > GABA. Octopamine is by far the most effective relaxing transmitter at this muscle. In accordance, the most effective octopamine antagonists, e.g. maroxepine and mianserin, are also the most effective inhibitors of the relaxation electrically evoked via transverse nerve 5. The pharmacological properties of the octopamine receptors lying on the hyperneural muscle indicate that they resemble the octopamine-1 class of receptors. The cholinergic antagonists scopolamine, azamethonium and atropine as well as the GABA-antagonists bicuculline, muscimol and baclofen were ineffective. None of the antagonists tested had any inhibiting or potentiating effect on the electrically via transverse nerve 7 evoked contractions of the muscle showing us that in this activating process biogenic amines or other “classic” transmitters are not integrated. Summarizing, we can conclude that the inactivating mediator at the hyperneural muscle is surely octopamine while the activating mediator is most probably proctolin.

Evidence for a myotropic effect of substance P in Periplaneta americana L

It is shown that the isolated oviduct as well as the proctodeum of the cockroach Periplaneta americana are sensitive to substance P application. In contrast, the hyperneural muscle and the dilator muscle of the antennal heart were insensitive to this neuropeptide. The entire substance P amino acid sequence is necessary for the effects. This provides evidence for a pharmacological effect of substance P in insects.

A pharmacological study of the hyperneural muscle of Periplaneta americana

Contractions of the hyperneural muscle of Periplaneta americana L., in response to various neurochemicals, were studied. Proctolin and glutamate were found to cause contractions, in a dosedependent manner. Octopamine, in the range of 1 μM to 1 mM suppressed chemically induced and neurally evoked contractions in a dose-dependent manner. Octopamine also reduced the basal tension of the muscle. Gamma aminobutyric acid (GABA), in the range of 100 μM to 1 mM also suppressed the neurally evoked hyperneural muscle contractions in a dose-dependent manner. GABA also reduced the basal tension of the muscle. Micromolar avermectin Bla abolished neurally evoked contractions. Although it is not known whether the neurochemicals have a physiological role in the hyperneural muscle function, it appears that the regulation of the muscle is not simple.

Electrophysiological studies of the effect of the neuropeptide proctolin on the hyperneural muscle of Periplaneta americana (L.)

The myotropic neuropeptide proctolin is, in additional to its action on proctodaeum and on some other systems, highly effective on the hyperneural muscle of Periplaneta americana and evokes long-term contractions. During this proctolin response the input resistance (R input) increases by about 25% accompanied by only slight depolarization. These processes require extracellular Ca 2+ but are still present in Na +-free solution. Junction potentials evoked by threshold stimulation of the nerve are not affected by proctolin. Synaptic processes do not seem to be important for the proctolin action on hyperneural muscle. It is more likely that the whole membrane of the muscle fibre serves as target for proctolin. Proctolin reduces the threshold for neurally evoked muscle contractions, the only available route of excitation since the muscle fibres themselves are not electrically excitable. The K +-channel blocker 4-aminopyridine may evoke contraction as well as proctolin, but this is only a transitory response. In contrast to proctolin, 4-aminopyridine is still effective after blocking the Ca 2+-channels by Co 2+, but the response is smaller. Therefore proctolin seems to be primarily effective via Ca 2+-channels, whereas 4-aminopyridine exerts its effects via K +-channels. The decrease in membrane conductance produced by proctolin could result from a Ca 2+-dependent reduction of the K +-outward current.

Chemical sensitivity of the hyperneural nerve-muscle preparation of the American cockroach

The hyperneural muscle of Periplaneta americana responded with sustained contracture to applications of l-glutamic acid at near 10 −4 M. d-glutamic acid was much less active. The responses of a particular preparation to glutamate were usually extremely consistent and highly reproducible; however, some preparations showed no response to l-glutamic acid even at 10 −2 M whereas neurally evoked responses were normal. High magnesium, low calcium perfused onto the preparations blocked neurally evoked contractions. The glutamate response was blocked reversibly in low calcium solutions. suggesting that the glutamate effect, when present, was presynaptic. Dopamine, acetylcholine, 5-hydroxytryptamine, synephrine, Rogitine ®, strychnine, strychnine, pentobarbital, and picrotoxin, all suspected to varying degrees of some action on insect central or peripheral synaptic transmission, had no effect on the patterns of neurally evoked contracture of the hyperneural muscle. A new transducer is described for use with low force insect muscle contractions.

Ultrastructure and electrical properties of the hyperneural muscle of Periplaneta americana

The hyperneural muscle of Periplaneta americana is striated with an A-band at least 2 μm long. Z-bands were discrete units, but arranged with some order in the myoplasm. The sarcoplasmic reticulum was reduced and 1 thick was surrounded by 10 to 12 thin myofilaments. The muscle is innervated from the median nerves by axons containing electron-dense granules which may be opaque near the neuromuscular junction amid numerous synaptic vesicles. Depolarizing intracellular current injection produces an ohmic voltage response of the membrane potential and neurally evoked contraction is effected by summated excitatory postsynaptic potentials. All contractal activity ceases when the innervation is removed. The muscle appears to be electrically inexcitable and to be under obligatory control of central motor units. By virtue of attachments along the ventral nerve cord in the abdomen, the hyperneural muscle, when activated, moves the nerve cord unidirectionally. In effect, the hyperneural muscle is called upon by the central nervous system to move the ventral nerve cord presumably into a greater mix with the haemolymph in response to as yet unknown stimuli.

Nerves and muscles of the pregenital abdominal segments of the American cockroach, Periplaneta americana (L.).

AbstractThe muscles and motor and sensory nerves of the pregenital abdominal segments were described and discussed in relation to the nerves and muscles of the thorax, as described by other workers. Each of the integumental muscles was named and described with regard to its location, function and innervation. Differences among segments of the same sex and between sexes were noted.A description of a longitudinal muscle, named here the hyperneural muscle, was included. The muscle overlies the abdominal portion of the nerve cord and may be derived from the ventral diaphragm. The most notable features of its structure are chiasmata of fibers which occur at points along its length and which show consistent relationships to the nerve cord and median nerve.A previously undescribed organ, located ventrally at the intersegmental fold, having dual innervation and showing stretch receptor function was described.