Plasticity and proprioception in insects. I. Responses and cellular properties of individual receptors of the locust metathoracic femoral chordotonal organ

1985 ◽  
Vol 116 (1) ◽  
pp. 435-461 ◽  
Author(s):  
S. N. Zill
Keyword(s):  
Joint Angle ◽  
Firing Frequency ◽  
Muscle Contractions ◽  
Current Injection ◽  
Chordotonal Organ ◽  
Muscle Fibres ◽  
Joint Position ◽  
Joint Movement ◽  
Single Action ◽  
Response Characteristics

The metathoracic femoral chordotonal organ is a joint angle receptor of the locust hindleg. It consists of 45–55 bipolar sensory neurones located distally in the femur and mechanically coupled to the tibia. Responses of receptors of the organ were examined by extracellular and intracellular recording. The organ as a whole encodes the angle of the femorotibial joint but shows substantial hysteresis. Tonic activity is greatest at the extremes of joint position. The organ possesses no direct linkage to tibial muscle fibres and shows no response to resisted muscle contractions in most ranges of joint angle. However, responses to extensor muscle contractions are obtained when the tibia is held in full flexion due to specializations of the femoro-tibial joint. These responses could be of importance in signalling preparedness for a jump. Intracellular soma recordings of activity in individual receptors indicate that the organ contains two types of receptors: phasic units that respond to joint movement and tonic units that encode joint position and also show some response to movement. All units are directionally sensitive and respond only in limited ranges of joint angle. Some phasic units increase firing frequency with increasing rate of movement and thus encode joint velocity. Other phasic units fire only single action potentials and can encode only the occurrence and direction of joint movement. All tonic units increase activity in the extremes of joint position and show substantial hysteresis upon return to more median positions. Direct soma depolarization produces different responses in different types of units: phasic receptors show only transient discharges to current injection; tonic receptors exhibit sustained increases in activity that are followed by periods of inhibition of background firing upon cessation of current injection. Receptors of the chordotonal organ are separable into two major groups, based upon their response characteristics, soma location and dendritic orientation: a dorsal group of receptors contains tonic units that respond in ranges of joint flexion (joint angle 0–80 degrees) and phasic units that respond to flexion movements; a ventral group of sensilla contains tonic units active in ranges of joint extension (joint angle 80–170 degrees) and phasic receptors that respond to extension movements. The response properties of these receptors are discussed with reference to the potential functions of the chordotonal organ in the locust's behavioural repertoire.

scholarly journals Plasticity and proprioception in insects. II. Modes of reflex action of the locust metathoracic femoral chordotonal organ

1985 ◽  
Vol 116 (1) ◽  
pp. 463-480
Author(s):  
S. N. Zill
Keyword(s):  
Joint Angle ◽  
Chordotonal Organ ◽  
Joint Movement ◽  
Reflex Responses ◽  
Support Resistance ◽  
Extensor Motoneurones ◽  
Excitatory Responses ◽  
Simple Summation ◽  
Stimulation Of ◽  
Active Searching

Reflex responses of tibial motoneurones were examined during mechanical stimulation of the femoral chordotonal organ, a joint angle receptor of the locust hindleg. Step displacements of the main ligament of the organ, mimicking 10–15 degree changes in joint angle, produced different patterns of discharge in motoneurones (1) when the leg was resting against a support and (2) when the support was removed to induce active searching movements. Tibial motoneurones showed resistance reflex responses to oppose the apparent joint movement when the leg rested against a support. Resistance reflexes consisted of constant, short latency excitatory responses followed by discharges that varied in intensity (gain) and degree of tonic coupling. These variations were not due to simple summation with other inputs to motoneurones. Responses changed during periods of active searching movements. Tibial flexor motoneurones fired phasically in response to apparent joint movement in any direction. Tibial extensor motoneurones were generally inhibited by chordotonal inputs. These reflex changes are not simple reflex ‘reversals’, but represent more complex changes in reflex mode. Potential functions of each of these reflex modes and the need for plasticity in reflexes of the chordotonal organ are discussed.

Complex Blockade of TTX-Resistant Na+ Currents by Lidocaine and Bupivacaine Reduce Firing Frequency in DRG Neurons

1998 ◽  
Vol 79 (4) ◽  
pp. 1746-1754 ◽  
Author(s):  
Andreas Scholz ◽  
Noboru Kuboyama ◽  
Gunter Hempelmann ◽  
Werner Vogel
Keyword(s):  
Spinal Anesthesia ◽  
Action Potentials ◽  
Sensory Information ◽  
Firing Frequency ◽  
Drg Neurons ◽  
Patch Clamp Technique ◽  
Single Action ◽  
Na Currents ◽  
Frequency Of Action Potentials ◽  
Frequency Of Stimulation

Scholz, Andreas, Noboru Kuboyama, Gunter Hempelmann, and Werner Vogel. Complex blockade of TTX-resistant Na+ currents by lidocaine and bupivacaine reduce firing frequency in DRG neurons. J. Neurophysiol. 79: 1746–1754, 1998. Mechanisms of blockade of tetrodotoxin-resistant (TTXr) Na+ channels by local anesthetics in comparison with the sensitivity of tetrodotoxin-sensitive (TTXs) Na+ channels were studied by means of the patch-clamp technique in neurons of dorsal root ganglions (DRG) of rat. Half-maximum inhibitory concentration (IC50) for the tonic block of TTXr Na+ currents by lidocaine was 210 μmol/l, whereas TTXs Na+ currents showed five times lower IC50 of 42 μmol/l. Bupivacaine blocked TTXr and TTXs Na+ currents more potently with IC50 of 32 and 13 μmol/l, respectively. In the inactivated state, TTXr Na+ channel block by lidocaine showed higher sensitivities (IC50 = 60 μmol/l) than in the resting state underlying tonic blockade. The time constant τ1 of recovery of TTXr Na+ channels from inactivation at −80 mV was slowed from 2 to 5 ms after addition of 10 μmol/l bupivacaine, whereas the τ2 value of ∼500 ms remained unchanged. The use-dependent block of TTXr Na+ channels led to a progressive reduction of current amplitudes with increasing frequency of stimulation, which was ≤53% block at 20 Hz in 10 μmol/l bupivacaine and 81% in 100 μmol lidocaine. The functional importance of the use-dependent block was confirmed in current-clamp experiments where 30 μmol/l of lidocaine or bupivacaine did not suppress the single action potential but clearly reduced the firing frequency of action potentials again with stronger potency of bupivacaine. Because it was found that TTXr Na+ channels predominantly occur in smaller sensory neurons, their blockade might underlie the suppression of the sensation of pain. Different sensitivities and varying proportions of TTXr and TTXs Na+ channels could explain the known differential block in spinal anesthesia. We suggest that the frequency reduction at low local anesthetic concentrations may explain the phenomenon of paresthesia where sensory information are suppressed gradually during spinal anesthesia.

scholarly journals Proprioceptive Acuity Assessment Via Joint Position Matching: From Basic Science to General Practice

2010 ◽  
Vol 90 (8) ◽  
pp. 1176-1184 ◽  
Author(s):  
Daniel J. Goble
Keyword(s):  
General Practice ◽  
Basic Science ◽  
Joint Angle ◽  
Critical Role ◽  
Clinical Settings ◽  
Proprioceptive Information ◽  
Joint Position ◽  
Subsequent Recovery ◽  
Dependent Plasticity ◽  
The Past

Over the past several decades, studies of use-dependent plasticity have demonstrated a critical role for proprioceptive feedback in the reorganization, and subsequent recovery, of neuromotor systems. As such, an increasing emphasis has been placed on tests of proprioceptive acuity in both the clinic and the laboratory. One test that has garnered particular interest is joint position matching, whereby individuals must replicate a reference joint angle in the absence of vision (ie, using proprioceptive information). On the surface, this test might seem straightforward in nature. However, the present perspective article informs therapists and researchers alike of multiple insights gained from a recent series of position matching studies by the author and colleagues. In particular, 5 factors are outlined that can assist clinicians in developing well-informed opinions regarding the outcomes of tests of position matching abilities. This information should allow for enhanced diagnosis of proprioceptive deficits within clinical settings in the future.

scholarly journals Small-Conductance Calcium-Activated Potassium Channels Control Excitability and Firing Dynamics in Gonadotropin-Releasing Hormone (GnRH) Neurons

Endocrinology ◽  
2008 ◽  
Vol 149 (7) ◽  
pp. 3598-3604 ◽  
Author(s):  
Xinhuai Liu ◽  
Allan E. Herbison
Keyword(s):  
Fluorescent Protein ◽  
Current Injection ◽  
Sk Channels ◽  
Cellular Mechanisms ◽  
Burst Frequency ◽  
Single Action ◽  
Sk Channel ◽  
Gnrh Neurons ◽  
Green Fluorescent ◽  
Small Conductance

The cellular mechanisms determining the firing patterns of GnRH neurons are presently under intense investigation. In this study, we used GnRH-green fluorescent protein transgenic mice and perforated-patch electrophysiology to examine the role of small conductance calcium-activated potassium (SK) channels in determining the electrical excitability and burst-firing characteristics of adult GnRH neurons. After establishing an appropriate protocol for examining the afterhyperpolarization potential (AHP) currents in GnRH neurons, the highly selective SK channel blocker apamin was used to demonstrate that all GnRH neurons express functional SK channels (35.7 ± 2.7 pA, mean decay time constant = 2167 msec, apamin IC50 = 9.6 nm) and that this channel underlies approximately 90% of the AHP in these cells. Current-clamp experiments showed that apamin-sensitive SK channels were tonically active in the majority (74%) of GnRH neurons, with apamin (100 nm) administration resulting in a mean 6.9 ± 0.5 mV membrane depolarization. Apamin also elevated the firing rate of GnRH neurons, including increased burst frequency and duration in spontaneously bursting cells as well as the ability of GnRH neurons to fire action potentials in response to current injection. In GnRH neurons activated by current injection, apamin significantly enhanced the amplitude of the afterdepolarization potential after a single action potential and eliminated spike frequency adaptation. Together, these studies show that apamin-sensitive SK channels play a key role in restraining GnRH neuron excitability. Through direct modulation of the AHP and indirect actions on the afterdepolarization potential, the SK channel exerts a powerful tonic influence upon the firing dynamics of GnRH neurons.

scholarly journals Proprioceptive Reflexes Change when an Insect Assumes an Active, Learned Posture

1983 ◽  
Vol 107 (1) ◽  
pp. 385-390
Author(s):  
SASHA N. ZILL ◽  
ROBIN R. FORMAN
Keyword(s):  
Joint Angle ◽  
Chordotonal Organ ◽  
Afferent Activity ◽  
Reflex Responses ◽  
Proprioceptive Reflexes ◽  
Receptor Input

Imposed changes in activity of a joint angle receptor of the locust leg, the metathoracic femoral chordotonal organ, produce variable, phasic reflex responses in a leg extensor motoneurone in untrained animals. After training the locust to maintain a posture in extension beyond a minimum required joint angle, these reflexes are consistently tonic and excitatory. This plasticity of reflex responsiveness permits the locust to couple motoneurone firing to afferent activity when receptor input is behaviourally relevant.

Low-Voltage-Activated Calcium Current Does Not Regulate the Firing Behavior in Paired Mechanosensory Neurons With Different Adaptation Properties

2000 ◽  
Vol 83 (2) ◽  
pp. 746-753 ◽  
Author(s):  
Shin-Ichi Sekizawa ◽  
Andrew S. French ◽  
Päivi H. Torkkeli
Keyword(s):  
Action Potential ◽  
Action Potentials ◽  
Low Voltage ◽  
Firing Frequency ◽  
Oscillatory Behavior ◽  
Firing Behavior ◽  
Single Action ◽  
Synaptic Excitation ◽  
Intracellular Ca ◽  
The Difference

Low-voltage-activated Ca2+ currents (LVA- I Ca) are believed to perform several roles in neurons such as lowering the threshold for action potentials, promoting burst firing and oscillatory behavior, and enhancing synaptic excitation. They also may allow rapid increases in intracellular Ca2+ concentration. We discovered LVA- I Ca in both members of paired mechanoreceptor neurons in a spider, where one neuron adapts rapidly (Type A) and the other slowly (Type B) in response to a step stimulus. To learn if I Ca contributed to the difference in adaptation behavior, we studied the kinetics of I Ca from isolated somata under single-electrode voltage-clamp and tested its physiological function under current clamp. LVA- I Ca was large enough to fire single action potentials when all other voltage-activated currents were blocked, but we found no evidence that it regulated firing behavior. LVA- I Ca did not lower the action potential threshold or affect firing frequency. Previous experiments have failed to find Ca2+-activated K+ current ( I K(Ca)) in the somata of these neurons, so it is also unlikely that LVA- I Ca interacts with I K(Ca) to produce oscillatory behavior. We conclude that LVA-Ca2+ channels in the somata, and possible in the dendrites, of these neurons open in response to the depolarization caused by receptor current and by the voltage-activated Na+ current ( I Na) that produces action potential(s). However, the role of the increased intracellular Ca2+ concentration in neuronal function remains enigmatic.

Serotonergic and Peptidergic Modulation of the Buccal Mass Protractor Muscle (I2) in Aplysia

2000 ◽  
Vol 84 (6) ◽  
pp. 2810-2820 ◽  
Author(s):  
I. Hurwitz ◽  
E. C. Cropper ◽  
F. S. Vilim ◽  
V. Alexeeva ◽  
A. J. Susswein ◽  
...  
Keyword(s):  
Muscle Contraction ◽  
Relaxation Rate ◽  
Behavioral Plasticity ◽  
Muscle Relaxation ◽  
Firing Frequency ◽  
Muscle Contractions ◽  
Contraction Amplitude ◽  
Neuronal Processes ◽  
Neuromuscular Systems ◽  
High Concentrations

Plasticity of Aplysia feeding has largely been measured by noting changes in radula protraction. On the basis of previous work, it has been suggested that peripheral modulation may contribute to behavioral plasticity. However, peripheral plasticity has not been demonstrated in the neuromuscular systems that participate in radula protraction. Therefore in this study we investigated whether contractions of a major radula protraction muscle (I2) are subject to modulation. We demonstrate, first, that an increase in the firing frequency of the cholinergic I2 motoneurons will increase the amplitude of the resulting muscle contraction but will not modulate its relaxation rate. We show, second, that neuronal processes on the I2 muscle are immunoreactive to myomodulin (MM), RFamide, and serotonin (5-HT), but not to small cardioactive peptide (SCP) or buccalin. The I2 motoneurons B31, B32, B61, and B62 are not immunoreactive to RFamide, 5-HT, SCP, or buccalin. However, all four cells are MM immunoreactive and are capable of synthesizing MMa. Third, we show that the bioactivity of the different modulators is somewhat different; while the MMs (i.e., MMa and MMb) and 5-HT increase I2 muscle relaxation rate, and potentiate muscle contraction amplitude, MMa, at high concentrations, depresses muscle contractions. Fourth, our data suggest that cAMP at least partially mediates effects of modulators on contraction amplitude and relaxation rate.

The Effect of Ice immersion on Joint Position Sense

1994 ◽  
Vol 3 (1) ◽  
pp. 58-67 ◽  
Author(s):  
Jane LaRiviere ◽  
Louis R. Osternig
Keyword(s):  
Joint Angle ◽  
Position Sense ◽  
Joint Position Sense ◽  
Joint Position ◽  
Protective Mechanisms ◽  
Sensory Stimuli ◽  
Skilled Performance ◽  
Significant Difference ◽  
Joint Receptors ◽  
Free Activity

Ice-induced anesthesia is often used to permit pain-free activity. However, icing before a skilled performance may distort the ability to acknowledge sensory stimuli and may thereby mask certain protective mechanisms. Inadequate peripheral feedback regarding position of a limb in space could expose the joint to injury. This study was designed to determine the effect of ice immersion on ankle joint position sense. Three different pretest conditions of no ice immersion, 5 min of ice immersion, and 20 min of ice immersion were administered to 31 subjects prior to joint angle replication testing with an electrogoniometer. Subjects completed eight repositioning trials (four at each of two test angles) following each condition. An analysis of variance (ANOVA) revealed no statistically significant difference between conditions, trials, or angles. The results suggest that joint position receptors in the ankle are resilient to this type of ice treatment, or that the affected receptors (i.e., skin and muscle) were adequately compensated for by other sensors such as joint receptors.

Proprioception in Patients With Anterior Cruciate Ligament Tears: A Meta-analysis Comparing Injured and Uninjured Limbs

2017 ◽  
Vol 45 (12) ◽  
pp. 2916-2922 ◽  
Author(s):  
Hyun-Jung Kim ◽  
Jin-Hyuck Lee ◽  
Dae-Hee Lee
Keyword(s):  
Anterior Cruciate Ligament ◽  
Cruciate Ligament ◽  
Meta Analysis ◽  
Joint Position Sense ◽  
Joint Position ◽  
Joint Movement ◽  
Mechanical Instability ◽  
Subgroup Analyses ◽  
The Mean ◽  
Anterior Cruciate

Background: Because of a reduction in the number of mechanoreceptors or alterations of their characteristics, anterior cruciate ligament (ACL) tears lead not only to mechanical instability but also to impaired proprioception. Purpose/Hypothesis: This study analyzed whether ACL tears cause a greater decrease in proprioception in injured than in uninjured knees. The hypothesis was that knee proprioception after ACL tears would decrease more in injured than in contralateral uninjured knees, regardless of the method used to measure knee proprioception. Study Design: Meta-analysis. Methods: We identified studies comparing proprioception in ACL-injured and contralateral intact knees using threshold for detection of passive motion (TTDPM) or joint position sense (JPS) tests. JPS was assessed by measuring the reproduction of passive positioning (RPP) or active repositioning (RAP) of the knee. Results: Sixteen studies were included in this meta-analysis. The pooled results of subgroup analyses of TTDPM for both 20° and 40° of knee flexion showed that mean angle of error was 0.23° (95% CI, 0.08°-0.37°) greater in ACL-injured than in contralateral intact knees ( P = .002). Pooled data RAP and RPP subgroup analyses also showed that the mean angle of error was 0.94° higher in ACL-injured than in contralateral intact knees. The mean difference in angle of error between ACL-injured and contralateral intact knees was 0.71° greater (95% CI, 0.68°-0.74°; P < .001) by JPS than by TTDPM. Conclusion: Proprioception of ACL-injured knees was decreased compared with contralateral intact knees, as determined by both joint movement (kinesthesia) and joint position. The magnitude of loss of proprioception was greater in joint position than in joint movement.

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