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H J Pflüger

Publications and source records attributed to H J Pflüger.

31 records · Page 2Linked to original sources
PubMed1992

Evidence for octopaminergic nature of peripherally projecting DUM-cells, but not DUM-interneurons in locusts.

In locusts, a median neuroblast in each segmental ganglion gives rise to numerous unpaired progeny--the well known peripherally projecting dorsal-, occasionally ventral-, unpaired median (DUM-, resp. VUM-) neurones together with the lesser known DUM-interneurones 12. We examine the reputed octopaminergic nature of this nerve cell lineage using an anti-octopamine serum recently developed by M. Eckert and J. Rapus 7. This antiserum labels in each segmental ganglion numerous midline neurones, identifiable as DUM- and VUM-cells by their some sizes and positions, projections in DUM-tracts and characteristic T-junctions with bilaterally projecting axons. All octopamine immunoreactive DUM-, and VUM-neurones appear to project to peripheral nerves; their numbers correspond to the number of peripherally projecting DUM- and VUM-neurones identified so far in the examined ganglia. Presumptive DUM-interneurones, i.e. smaller somata interspersed between the peripherally projecting DUM-cells are not octopamine immunoreactive, but, confirming other studies 25, display GABA-like immunoreactivity. We thus suggest, that of the whole DUM-cell population in the examined ganglia, all and only peripherally projecting DUM-neurons are octopaminergic.

Animals↗
PubMed1990

Bilaterally projecting neurones in pregenital abdominal ganglia of the locust: anatomy and peripheral targets.

The anatomy and physiology of neurones with axons in left and right homologous nerves was studied in abdominal ganglia of the migratory locust, Locusta migratoria, by using a differential cobalt/nickel staining method. These neurones reside within two clusters at the anterior and posterior ends of all unfused abdominal ganglia. Each cluster contains at least seven neurones with bilaterally projecting axons. All neurones of the anterior cluster possess bilaterally projecting axons which leave the ganglion through nerve 2 (= sternal nerve) or nerve 1 (= tergal nerve). Additional axon collaterals, which are present in some of these neurones leave through either nerve 1 or nerve 2 of the right or left side of the ganglion. With few exceptions, the neurones show further asymmetries in their dendritic arborizations. Neurones of the posterior group also have bilaterally projecting axons that leave the ganglion through nerve 1 or nerve 2. Among these neurones are the two large posterior dorsal unpaired median (DUM) neurones with bilaterally symmetrical axons that were described earlier as DUM1 and DUM2. They innervate the skeletal muscles of an abdominal segment. Two other cells of this cluster have anatomical properties similar to the DUM1 neurone and were termed DUMheart1A and DUMheart1B. The rest resemble the bilaterally projecting neurones of the anterior group. With the exception of the two classic DUM neurones (DUM1 and DUM2), all neurones of the anterior and posterior cluster innervate the heart or a neurohaemal area.

Animals↗
PubMed1989

Regional specialisation for synaptic input and output on a locust intersegmental interneurone with multiple spike-initiating zones.

A4I1 is a long intersegmental interneurone whose soma lies in the fourth abdominal ganglion and whose axon ascends through, and branches in, the thoracic and suboesophageal ganglia and the brain. It receives sensory input in the prothoracic ganglion from wind-sensitive hairs on the head and prosternum and in the fourth abdominal ganglion from cercal afferents (Pflüger: J. Comp. Neurol. 222:343-357, '84). Spikes can be initiated from both of these ganglia. In the present study the neurone was stained by intracellular injection of cobalt salts for light microscopy and of horseradish peroxidase for electron microscopy. The morphology of its neurites in the thoracic and fourth abdominal ganglia and the distribution of synapses upon them could then be observed and correlated. In the fourth abdominal ganglion the neurone receives input synapses but makes no outputs. In each thoracic ganglion the neurone has fine, varicose ventral neurites and thicker dorsal neurites. The ventral neurites are most abundant in the prothoracic ganglion where they receive only input synapses. In the meso- and metathoracic ganglia the ventral neurites also receive inputs, but in addition they make output synapses. In all three thoracic ganglia output synapses are abundant on the dorsal branches, but in the meso- and metathoracic ganglia a small number of inputs are also received here. The possibility that the function of the interneurone may not be the same in all of the thoracic ganglia is discussed in the light of its known physiological properties.

Action Potentials↗
PubMed1988

Structure and distribution of dorsal unpaired median (DUM) neurones in the abdominal nerve cord of male and female locusts.

Dorsal unpaired median (DUM) neurones in insects have been shown to modulate the activity of both skeletal and visceral muscle. It has been suggested that as a population they carry out a role analogous to that of the sympathetic nervous system in vertebrates; however, the extent of their distribution throughout the ventral nerve cord has not been assessed. This paper aims to fill this gap by systematically describing the number and morphology of DUM neurones in each of the abdominal ganglia of male and female locusts. To achieve this, the lateral nerves of each abdominal ganglion were backfilled to reveal the position of the somata of DUM neurones. To confirm their identity and reveal their structure, DUM somata were then impaled with microelectrodes and, after physiological characterization, the neurones were stained by intracellular injection with cobalt ions. In each of the first six abdominal ganglia of both sexes, two DUM neurones, one with axons in the tergal nerve and one with axons in the sternal nerve, were found. In the seventh abdominal, and the terminal, ganglion (composed of the eighth to eleventh neuromeres), there was considerable sexual dimorphism in DUM neurone distribution, which was most marked in those associated with some of the nerves innervating the genitalia. In the male, four clusters of somata in the seventh, eighth, and tenth segments have axons in the genital nerve. In the female, which lacks a genital nerve, clusters of DUM neurones, absent in the male, have axons in the seventh and eighth sternal nerves and the cercal nerve.

Animals↗
PubMed1987

A strand receptor with a central cell body synapses upon spiking local interneurones in the locust.

Movements of the femoro-tibial joint of a locust hind leg are monitored by three classes of proprioceptors; a chordotonal organ (Usherwood et al. 1968), multipolar joint receptors (Coillot and Boistel 1968) and a strand receptor innervated by a single afferent with a central cell body (Bräunig 1985). All three classes are excited by imposed or voluntary extension of the tibia. The strand receptor (fe-tiSR) spikes tonically and at a frequency dependent upon the position of the joint whilst the multipolar joint receptors give overlapping information but for a more restricted range. The afferent from the strand receptor makes an excitatory connection with a spiking local interneurone in the midline group of the metathoracic ganglion. The central latency and consistency with which the EPSP follows each sensory spike suggests that the connection is direct. This interneurone also receives convergent inputs from neurones in the chordotonal organ, but not from multipolar joint receptors. Neither the strand receptor nor the multipolar joint receptors apparently synapse upon leg motor neurones that we have tested, in contrast to receptors in the chordotonal organ.

Animals↗
PubMed1986

Processing by local interneurons of mechanosensory signals involved in a leg reflex of the locust.

At the distal end of the tibia of a locust hind leg are 2 pairs of movable spurs that can be moved by contact with external objects--as, for example, when the body sways from side to side and loads one leg unevenly or when the foot is placed on rough ground--but not by direct muscular action. Movements imposed on a spur evoke phasic bursts of spikes in the axon of a single receptor cell at its base. If the displacement is maintained, however, the response adapts within a few seconds. The afferents from these spur receptors excite particular spiking local interneurons with cell bodies at the ventral midline of the metathoracic ganglion. Each afferent spike is consistently followed at a constant latency by a depolarizing potential in one of these interneurons. The potential can evoke a spike, and its amplitude is enhanced by a hyperpolarization applied to the interneuron. The central delay to this chemically mediated EPSP, which also includes conduction time to synaptic sites, probably indicates a direct connection. Some spiking local interneurons are excited by the 2 anterior spurs but are unaffected by the 2 posterior ones, while others receive the converse pattern of inputs. The receptive fields of these interneurons also include regions on either the anterior or posterior surfaces of the tibia with excitatory inputs from hair afferents. A reliable inhibitory reflex effect on the single levator tarsi is evoked by movement of any of the 4 spurs. The inhibitory potentials are not caused directly by the sensory afferents but involve the spiking local interneurons upon which the afferents synapse. The receptive field of this motor neuron therefore results from the convergence of inputs from a few interneurons. Motor neurons of other tarsal muscles are unaffected by movement of the spurs, but those of some more proximal muscles may be excited. These reflex effects should enhance the traction of the tarsus with the ground.

Afferent Pathways↗
PubMed1984

The large fourth abdominal intersegmental interneuron: a new type of wind-sensitive ventral cord interneuron in locusts.

A large interneuron in Locusta migratoria is described that extends from the fourth abdominal ganglion to the brain. The morphology was revealed by injection of cobaltous ions or Lucifer yellow into the cell. As its cell body lies within the fourth abdominal ganglion it is named A4I1, the first-identified intersegmental interneuron of the fourth abdominal ganglion. This neuron receives input from highly flexible, wind-sensitive hairs on the prosternum, the pronotum, and the head (field 1). Sensory connections with A4I1 are made within the prothoracic ganglion. Stimulation of the receptive field initiates spikes in A4I1 which travel anteriorly and posteriorly from the prothoracic ganglion. Intracellular recording from the axon and the soma shows that the cell membrane becomes inactive within the fourth abdominal ganglion. Spikes could be generated within the fourth abdominal ganglion by current injection into the soma. Occasionally excitatory postsynaptic potentials were observed in a soma recording, but up to now there is no evidence for a second spike initiation site. By intracellular current injection into the soma of the left and right A4I1 cell it is shown that the two cells are not electrically coupled.

Afferent Pathways↗
PubMed1984

Proprioceptor distribution and control of a muscle reflex in the tibia of spider legs.

In spiders, retrograde cobalt staining was used to clarify the distribution and detailed innervation of the three types of proprioceptors in the tibio-metatarsal leg joint: internal joint receptors, lyriform slit sense organs, and cuticular spines and hairs. The axons of all these receptors run in just two lateral, ascending nerves, which had previously been associated only with the internal receptors. Each nerve contains several hundred axons ranging in diameter from 0.1 micron to ca. 10 micron. Each slit of the four tibial lyriform organs is innervated by two bipolar sensory neurons. The lateral nerves are entirely sensory and run just beneath the cuticle, a convenient site for electrophysiological recording. We demonstrate simultaneous nerve and muscle recordings from intact spiders; these, in combination with selective sensory ablations, show that a resistance reflex in the flexor metatarsi muscles is elicited by internal joint-receptor units.

Animals↗
PubMed1984

The ultrastructure of prosternal sensory hair afferents within the locust central nervous system.

The sensory neurones innervating long prosternal hairs of Locusta migratorioides were backfilled with horseradish peroxidase through their dendrites. The neurones' central projections in and around the medial ventral tract were examined with electron microscopy. Most synapses occur on axon collaterals which ramify through the neuropile around the tract where both input and output synapses were observed. Serial sectioning methods were used to determine the relative distribution of inputs and outputs which often lie in close proximity to one another on the axon terminals. The prosternal hair terminals contain agranular synaptic vesicles approximately 37 nm in diameter. Surrounding unidentified neuropilar profiles contain vesicles which are either statistically indistinguishable in size, or are larger, 45 nm diameter agranular vesicles. Neurones which are pre- or postsynaptic to labelled terminals generally contain vesicles of the second type. Input synapses onto the central terminals of primary afferent neurones can be recognised as a widespread phenomenon in the nervous systems of both invertebrates and vertebrates which will allow a fine degree of control of sensory inflow into the central nervous system.

Animals↗
PubMed1983

The specificity of central nervous projections of locust mechanoreceptors.

The central projections of hairplates and groups of campaniform sensilla of various parts of the locust head, neck, and thorax are compared. Receptors with approximately the same peripheral location (e.g., dorsal head, wing, or proximal leg) tend to exhibit similar central projection patterns. Specificity of the projections due to different morphological types of sensory neurones may influence shape and extent of segmental ramifications; this is observed with receptors of the proximal leg joints in particular.

Animals↗
PubMed1981

Distribution and specific central projections of mechanoreceptors in the thorax and proximal leg joints of locusts. I. Morphology, location and innervation of internal proprioceptors of pro- and metathorax and their central projections.

The mechanoreceptive supply of ventral thoracic parts and proximal leg joints of the pro- and metathorax of two locust species has been studied with the help of a modification of the axonal infusion technique with cobaltous chloride, which permits staining of the peripheral nervous system of an entire segment. The number, location, and innervation of serially homologous chordotonal organs (CO), strand receptors (SR), multipolar sensilla (MS), hair plates (HP) and clustered campaniform sensilla (CS) are described, as well as population specific central projections of primary afferent fibers from internal receptors (CO, MS). CO projections tend to form intersegmental projections within the thoracic ganglia, the extent varying with the organ's location. Apart from dorso-lateral collaterals, they terminate mainly in the medioventral neuropile, where they also cross the longitudinal midline of the CNS. By contrast, MS projections stay ipsilateral and do not leave their ganglia, where they send collaterals into all levels of the neuropile.

Animals↗
PubMed1981

Distribution and specific central projections of mechanoreceptors in the thorax and proximal leg joints of locusts. II. The external mechanoreceptors: hair plates and tactile hairs.

Tactile hairs on the locust thorax can be divided into two classes by their external morphology and their central projection pattern: Short hairs, 10--100 micrometer in length, which are assembled in distinct plates and rows, and long hairs, 100--800 micrometer in length, which are distributed all over the body and are organized in large fields or aligned along the ridges of the appendages. The sensory fibers of the first class arborize in the lateral dorsal neuropile of thoracic ganglia and then extend further into the ipsilateral half of the corresponding ganglion in three main bundles from which fine rami of fibers end in the intermediate neuropile. In all three thoracic ganglia the projection pattern of homologous hair plates is similar. The sensory fibers of the second class exclusively terminate in special median ventral neuropiles, the ventral association center (VAC) and ventralmost ventral association center (VVAC). In addition fibers from meso- and metathoracic hairs, located close to the longitudinal midline of the animal, may terminate in the contralateral VAC and with one branch project to the next anterior ganglion through the ipsilateral connective. In contrast, fibers from prothoracic hairs were not found to leave their ganglion.

Animals↗