Multimodal Convergence of Presynaptic Afferent Inhibition in Insect Proprioceptors

1999 ◽  
Vol 82 (1) ◽  
pp. 512-514 ◽  
Author(s):  
Wolfgang Stein ◽  
Josef Schmitz
Keyword(s):  
Presynaptic Inhibition ◽  
Sensory Information ◽  
Reversal Potential ◽  
Stick Insect ◽  
Chordotonal Organ ◽  
Primary Afferent Depolarization ◽  
Campaniform Sensilla ◽  
Sense Organs ◽  
Position Sensitive ◽  
Conductance Increase

In the leg motor system of insects, several proprioceptive sense organs provide the CNS with information about posture and movement. Within one sensory organ, presynaptic inhibition shapes the inflow of sensory information to the CNS. We show here that also different proprioceptive sense organs can exert a presynaptic inhibition on each other. The afferents of one leg proprioceptor in the stick insect, either the position-sensitive femoral chordotonal organ or the load-sensitive campaniform sensilla, receive a primary afferent depolarization (PAD) from two other leg proprioceptors, the campaniform sensilla and/or the coxal hairplate. The reversal potential of this PAD is about −59 mV, and the PAD is associated with a conductance increase. The properties of this presynaptic input support the hypothesis that this PAD acts as presynaptic inhibition. The PAD reduces the amplitude of afferent action potentials and thus likely also afferent transmitter release and synaptic efficacy. These findings imply that PAD mechanisms of arthropod proprioceptors might be as complex as in vertebrates.

Inhibition of mechanosensory interneurons in the crayfish. I. Presynaptic inhibition from giant fibers

1980 ◽  
Vol 43 (6) ◽  
pp. 1495-1509 ◽  
Author(s):  
D. Kennedy ◽  
J. McVittie ◽  
R. Calabrese ◽  
R. A. Fricke ◽  
W. Craelius ◽  
...  
Keyword(s):  
Reversal Potential ◽  
Repetitive Firing ◽  
Primary Afferent Depolarization ◽  
Gamma Aminobutyric Acid ◽  
Giant Axons ◽  
Pharmacological Studies ◽  
Sucrose Gap ◽  
Conductance Increase ◽  
Tail Flip ◽  
Stimulation Of

1. Sucrose-gap and intracellular recordings were used to study the primary afferent depolarization (PAD) produced in mechanosensory afferents by impulses in lateral and medial giant axons, which are the command cells for the tail flip escape response in the crayfish. 2. The lateral and medial giant axons produce PAD through a polysynaptic interneuronal pathway. The response has a relatively long intraganglionic latency (7--11 ms), and command-evoked PAD can be recorded in ganglia from which the giant axons have been experimentally disconnected. 3. The final neurons of the pathway that delivers inhibition are few in number and extensive in distribution; most appear to be common to lateral and medial giant pathways. 4. At least some of the inhibitory interneurons have axons in the interganglionic connectives and probably produce both presynaptic and postsynaptic inhibition. 5. Stimulation of the lateral, but not the medial, giant axons causes a small, short-latency deplorization that is stable at high repetition rates. This small potential can be accounted for by transmission across known electrical synapses between mechanosensory afferents and the lateral giants in each abdominal ganglion. 6. Repetitive stimulation of the lateral giant axons causes substantial augmentation of PAD, apparently through recruitment of additional interneurons. PAD evoked by a single medial giant (MG) stimulus is generally much larger than that elicited by a single lateral giant (LG) spike. However, MG-PAD summates little and so the maximum PAD deltaV reached during repetitive firing is equivalent for the two types of giant axons. 7. Iontophoresis of gamma-aminobutyric acid (GABA) into the ganglionic neuropil depolarizes the primary afferents and blocks activity in neurons that have axons in the interganglionic connective. 8. The extrapolated PAD reversal potential and pharmacological studies suggest that a GABA-mediated chloride conductance increase is involved in the production of PAD.

scholarly journals FUNCTIONAL SPECIALIZATION OF THE SCOLOPARIA OF THE FEMORAL CHORDOTONAL ORGAN IN STICK INSECTS

1992 ◽  
Vol 173 (1) ◽  
pp. 91-108 ◽  
Author(s):  
R. Kittmann ◽  
J. Schmitz
Keyword(s):  
Stick Insect ◽  
Sensory Cells ◽  
Chordotonal Organ ◽  
Functional Specialization ◽  
Control Loop ◽  
Sense Organs ◽  
Stick Insects ◽  
Extensor Motoneurones

The femoral chordotonal organ (fCO), one of the largest proprioceptive sense organs in the leg of the stick insect, is important for the control of the femur-tibia joint during standing and walking. It consists of a ventral scoloparium with about 80 sensory cells and a dorsal scoloparium with about 420 sensory cells. The present study examines the function of these scoloparia in the femur-tibia control loop. Both scoloparia were stimulated independently and the responses in the extensor tibiae motoneurones were recorded extra- and intracellularly. The ventral scoloparium, which is the smaller of the two, functions as the transducer of the femur-tibia control loop. Its sensory cells can generate the known resistance reflexes. The dorsal scoloparium serves no function in the femur-tibia control loop and its stimulation elicited no or only minor reactions in the extensor motoneurones. A comparison with other insect leg proprioceptors shows that a morphological subdivision of these organs often indicates a functional specialization.

Nonspiking Pathways in a Joint-control Loop of the Stick Insect Carausius Morosus

1990 ◽  
Vol 151 (1) ◽  
pp. 133-160 ◽  
Author(s):  
ANSGAR BÜSCHGES
Keyword(s):  
Sensory Information ◽  
Stick Insect ◽  
Chordotonal Organ ◽  
Joint Control ◽  
Control Loop ◽  
Carausius Morosus ◽  
Extensor Motoneurones ◽  
Reflex Activation ◽  
Flexion And Extension ◽  
Stimulation Of

In the stick insect Carausius morosus (Phasmida) intracellular recordings were made from local nonspiking interneurones involved in the reflex activation of the extensor motoneurones of the femur-tibia joint during ramp-like stimulation of the transducer of this joint, the femoral chordotonal organ (ChO). The nonspiking interneurones in the femur-tibia control loop were characterized by their inputs from the ChO, their output properties onto the extensor motoneurones and their morphology. Eight different morphological and physiological types of nonspiking interneurones are described that are involved in the femur-tibia control loop. The results show that velocity signals from the ChO are the most important movement parameter processed by the nonspiking interneurones. Altering the membrane potential of these interneurones had marked effects on the reflex activation in the extensor motoneurones as the interneurones were able to increase or decrease the response of the participating motoneurones. The processing of information by the nonspiking pathways showed another remarkable aspect: nonspiking interneurones were found to process sensory information from the ChO onto extensor motoneurones in a way that seems not always to support the generation of the visible resistance reflexes in the extensor tibiae motoneurones in response to imposed flexion and extension movements of the joint. The present investigation demonstrated interneuronal pathways in the joint-control loop that show ‘assisting’ characteristics.

Control of reflex reversal in stick insect walking: effects of intersegmental signals, changes in direction, and optomotor-induced turning

2012 ◽  
Vol 107 (1) ◽  
pp. 239-249 ◽  
Author(s):  
Katja Hellekes ◽  
Eric Blincow ◽  
Julia Hoffmann ◽  
Ansgar Büschges
Keyword(s):  
Nervous System ◽  
Sensory Feedback ◽  
Stick Insect ◽  
Chordotonal Organ ◽  
Sense Organs ◽  
Carausius Morosus ◽  
Output Change ◽  
Reflex Reversal ◽  
Leg Movement ◽  
First Time

In many animals, the effects of sensory feedback on motor output change during locomotion. These changes can occur as reflex reversals in which sense organs that activate muscles to counter perturbations in posture control instead reinforce movements in walking. The mechanisms underlying these changes are only partially understood. As such, it is unclear whether reflex reversals are modulated when locomotion is adapted, such as during changes in walking direction or in turning movements. We investigated these questions in the stick insect Carausius morosus, where sensory signals from the femoral chordotonal organ are known to produce resistance reflexes at rest but assistive movements during walking. We studied how intersegmental signals from neighboring legs affect the generation of reflex reversals in a semi-intact preparation that allows free leg movement during walking. We found that reflex reversal was enhanced by stepping activity of the ipsilateral neighboring rostral leg, whereas stepping of contralateral legs had no effect. Furthermore, we found that the occurrence of reflex reversals was task-specific: in the front legs of animals with five legs walking, reflex reversal was generated only during forward and not backward walking. Similarly, during optomotor-induced curved walking, reflex reversal occurred only in the middle leg on the inside of the turn and not in the contralateral leg on the outside of the turn. Thus our results show for the first time that the nervous system modulates reflexes in individual legs in the adaptation of walking to specific tasks.

Presynaptic inhibition is mediated by histamine and GABA in the crustacean escape reaction

1994 ◽  
Vol 71 (3) ◽  
pp. 1088-1095 ◽  
Author(s):  
A. el Manira ◽  
F. Clarac
Keyword(s):  
Presynaptic Inhibition ◽  
Reversal Potential ◽  
Membrane Conductance ◽  
Chordotonal Organ ◽  
Gamma Aminobutyric Acid ◽  
Giant Fiber ◽  
Sensory Transmission ◽  
Gaba Antagonist ◽  
Escape Reaction

1. Presynaptic inhibition of sensory transmission during the escape reaction in Crustacea has been studied using an in vitro preparation of the crayfish thoracic ganglia. Electrical stimulation of the medial giant fiber mediating the escape reaction induced depolarization in sensory afferent terminals of the coxo-basal chordotonal organ (CBCO). This depolarization was associated with an increase of the membrane conductance and was partially blocked by a gamma-aminobutyric acid (GABA) antagonist, picrotoxin, and by a histamine antagonist, cimetidine. 2. Pressure ejection of histamine on CBCO sensory terminals (CBT) recorded intracellularly, induced a depolarization of the membrane potential accompanied by a large increase of the conductance. Histamine-induced depolarization persisted after blockade of synaptic transmission mediated by Na+ spikes by tetrodotoxin. The amplitude of histamine-induced depolarization increased when negative current was injected into the sensory terminal through the recording electrode. Moreover, injection of chloride into the CBT, which shifts the reversal potential of chloride to a more positive value, resulted in an increase of the amplitude of the histamine-induced depolarization. 3. The existence of separate receptors for GABA and histamine on the CB sensory terminals was demonstrated using two complementary sets of experiments. The first one consisted of using specific blockers of GABA and histamine. Picrotoxin blocked selectively the GABA-induced depolarization of the CB sensory terminals, while it was ineffective in blocking the histamine-induced depolarization. Conversely, cimetidine blocked the histamine-induced depolarization totally, but did not affect the GABA response. The second set of experiments tested for of cross-desensitization between GABA and histamine responses.(ABSTRACT TRUNCATED AT 250 WORDS)

scholarly journals THE PHYSIOLOGY OF SENSORY CELLS IN THE VENTRAL SCOLOPARIUM OF THE STICK INSECT FEMORAL CHORDOTONAL ORGAN

1994 ◽  
Vol 189 (1) ◽  
pp. 285-292 ◽  
Author(s):  
A Büschges
Keyword(s):  
Sensory Feedback ◽  
Neural Control ◽  
Sensory Information ◽  
Stick Insect ◽  
Sensory Cells ◽  
Chordotonal Organ ◽  
Joint Movement ◽  
Control Loop ◽  
Sensory Neurones ◽  
Control Loops

The leg joints of invertebrates are governed by neural control loops that control their position and velocity during movements (for reviews, see Bassler, 1983, 1993). These neural control loops rely on sensory feedback about the position and velocity of the controlled leg joint. In invertebrates, this sensory feedback is provided by external (e.g. hair fields, hair rows) and/or internal sense organs (e.g. chordotonal organs). The femoral chordotonal organ (fCO) serves as the main proprioceptor in the control loop governing the femur-tibia (FT) joint of the insect leg. The fCO measures the position and movement of this joint (e.g. Bassler, 1965, 1993; Burns, 1974; Usherwood et al. 1968; Zill, 1985). Previous investigations have described the physiology of sensory cells within femoral chordotonal organs (e.g. stick insect, Hofmann et al. 1985; Hofmann and Koch, 1985; locust, Matheson, 1990; Matheson and Field, 1990). Numerous investigations have been undertaken into the central processing of sensory information provided by the fCO to gain an insight into the control of FT joint movement during different behavioural tasks, for example during resistance reflexes in the standing animal (locust, Burrows, 1987, 1988; Burrows et al. 1988; stick insect, Bassler, 1988; Buschges, 1989, 1990; Driesang and Buschges, 1993) or during active movements (stick insect, Bassler, 1988; Bassler and Buschges, 1990). Most previous studies have not, however, taken into account the morphological separation of the fCO into two distinct scoloparia in the legs of some species (stick insect, Fuller and Ernst, 1973; Hofmann et al. 1985; Hofmann and Koch, 1985; locust middle leg, Burns, 1974). It has been inferred that the whole fCO supplies position and velocity information about the FT joint. In contrast, recent studies of leg reflexes have shown that only its smaller scoloparium (Fig. 1A), containing approximately one-sixth of the total number of sensory neurones, provides the sensory information that is used by the FT control loop (locust, Field and Pfluger, 1989; stick insect, Kittmann and Schmitz, 1992). These studies did not show what types of sensory neurones are located in the ventral part of the fCO and thus contribute to the FT control loop. We have therefore investigated the physiology of sensory neurones that are located in the ventral scoloparium of the fCO.

Characterization of synaptically mediated fast and slow inhibitory processes in piriform cortex in an in vitro slice preparation

1988 ◽  
Vol 59 (5) ◽  
pp. 1352-1376 ◽  
Author(s):  
G. F. Tseng ◽  
L. B. Haberly
Keyword(s):  
Membrane Potential ◽  
Piriform Cortex ◽  
Reversal Potential ◽  
Pyramidal Cells ◽  
Membrane Depolarization ◽  
Resting Membrane Potential ◽  
Excitatory Postsynaptic Potential ◽  
Pentobarbital Sodium ◽  
Postsynaptic Potential ◽  
Conductance Increase

1. Intracellular recordings were obtained from anatomically verified layer II pyramidal cells in slices from rat piriform cortex cut perpendicular to the surface. 2. Responses to afferent and association fiber stimulation at resting membrane potential consisted of a depolarizing potential followed by a late hyperpolarizing potential (LHP). Membrane polarization by current injection revealed two components in the depolarizing potential: an initial excitatory postsynaptic potential (EPSP) followed at brief latency by an inhibitory postsynaptic potential (IPSP) that inverted with membrane depolarization and truncated the duration of the EPSP. 3. The early IPSP displayed the following characteristics suggesting mediation by gamma-aminobutyric acid (GABA) receptors linked to Cl- channels: associated conductance increase, sensitivity to increases in internal Cl- concentration, blockage by picrotoxin and bicuculline, and potentiation by pentobarbital sodium. The reversal potential was in the depolarizing direction with respect to resting membrane potential so that the inhibitory effect was exclusively via current shunting. 4. The LHP had an associated conductance increase and a reversal potential of -90 mV in normal bathing medium that shifted according to Nernst predictions for a K+ potential with changes in external K+ over the range 4.5-8 mM indicating mediation by the opening of K+ channels and ruling out an electrogenic pump origin. 5. Lack of effect of bath-applied 8-bromoadenosine 3',5'-cyclic monophosphate (8-Br-cAMP) or internally applied ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid (EGTA) on the LHP and failure of high amplitude, direct membrane depolarization to evoke a comparable potential, argue against endogenous mediation of the LHP by a Ca2+ activated K+ conductance [gK(Ca)]. However, an apparent endogenously mediated gK(Ca) with a duration much greater than the LHP was observed in a low percent of layer II pyramidal cells. Lack of effect of 8-Br-cAMP also indicates a lack of dependence of the LHP on cAMP. 6. Other characteristics of the LHP that were demonstrated include: a lack of blockage by GABAA receptor antagonists, a probable voltage sensitivity (decrease in amplitude in the depolarizing direction), and an apparent brief onset latency (less than 10 ms) when the early IPSP was blocked by picrotoxin. The LHP was unaffected by pentobarbital sodium when the early IPSP was blocked by picrotoxin. 7. Both the LHP and early IPSP were blocked by low Ca2+/high Mg2+, consistent with disynaptic mediation.(ABSTRACT TRUNCATED AT 400 WORDS)

Whole cell current analyses of pancreatic acinar AR42J cells. I. Voltage- and Ca(2+)-activated currents

1991 ◽  
Vol 260 (5) ◽  
pp. C934-C948 ◽  
Author(s):  
K. Kusano ◽  
H. Gainer
Keyword(s):  
Reversal Potential ◽  
Outward Current ◽  
Pancreatic Acinar Cells ◽  
Equilibrium Potential ◽  
Channel Blockers ◽  
Whole Cell ◽  
Inward Current ◽  
Tail Current ◽  
Ar42j Cells ◽  
Conductance Increase

Voltage- and Ca(2+)-activated whole cell currents were studied in AR42J cells, a clonal cell line derived from rat pancreatic acinar cells, using a patch electrode voltage-clamp technique. Four kinds of ionic currents were identified by their ionic dependencies, pharmacological properties, and kinetic parameters: 1) an outward current flow due mainly to a voltage-dependent K(+)-conductance increase, 2) an initial transient inward current due to an Na(+)-conductance increase, 3) transient and long-duration inward current due to a Ca(2+)-conductance increase, and 4) a slowly activating inward current that persists over the duration of the depolarizing pulse and deactivates slowly upon repolarization, producing a slow inward tail current. The slow inward tail current was particularly robust and was interpreted as due to a Ca(2+)-activated Cl(-)-conductance increase, since 1) the generation of this current was blocked by removing the extracellular Ca2+, applying Ca(2+)-channel blockers (Cd2+, nifedipine), or by lowering the intracellular Ca2+ concentration [( Ca2+]i) with EGTA; and 2) the reversal potential (Erev) of the slow inward tail current was close to 0 mV in the control condition (152 mM [Cl-]o/154 mM [Cl-]i), and changes of the [Cl-]o/[Cl )i ratio shifted the Erev toward the predicted Cl- equilibrium potential.

Intersegmental Coordination of Walking Movements in Stick Insects

2005 ◽  
Vol 93 (3) ◽  
pp. 1255-1265 ◽  
Author(s):  
Björn Ch. Ludwar ◽  
Marie L. Göritz ◽  
Joachim Schmidt
Keyword(s):  
Motor Pattern ◽  
Central Pattern Generators ◽  
Stick Insect ◽  
Neural Mechanisms ◽  
Chordotonal Organ ◽  
Adjacent Segment ◽  
Body Segments ◽  
Stick Insects ◽  
Pattern Generators ◽  
Leg Movements

Locomotion requires the coordination of movements across body segments, which in walking animals is expressed as gaits. We studied the underlying neural mechanisms of this coordination in a semi-intact walking preparation of the stick insect Carausius morosus. During walking of a single front leg on a treadmill, leg motoneuron (MN) activity tonically increased and became rhythmically modulated in the ipsilateral deafferented and deefferented mesothoracic (middle leg) ganglion. The pattern of modulation was correlated with the front leg cycle and specific for a given MN pool, although it was not consistent with functional leg movements for all MN pools. In an isolated preparation of a pair of ganglia, where one ganglion was made rhythmically active by application of pilocarpine, we found no evidence for coupling between segmental central pattern generators (CPGs) that could account for the modulation of MN activity observed in the semi-intact walking preparation. However, a third preparation provided evidence that signals from the front leg's femoral chordotonal organ (fCO) influenced activity of ipsilateral MNs in the adjacent mesothoracic ganglion. These intersegmental signals could be partially responsible for the observed MN activity modulation during front leg walking. While afferent signals from a single walking front leg modulate the activity of MNs in the adjacent segment, additional afferent signals, local or from contralateral or posterior legs, might be necessary to produce the functional motor pattern observed in freely walking animals.

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