scholarly journals Development of sensory processes during limb regeneration in adult crayfish.

1998 ◽  
Vol 201 (11) ◽  
pp. 1745-1752
Author(s):  
R L Cooper
Keyword(s):  
Sensory Neurons ◽  
Motor Neurons ◽  
Normal Development ◽  
Procambarus Clarkii ◽  
Limb Regeneration ◽  
Growth Cones ◽  
Neural Regeneration ◽  
Segmental Ganglion ◽  
Sensory Processes ◽  
Sensory Endings

The capacity of the crayfish Procambarus clarkii to regenerate its walking legs provides a system for studying the mechanisms of neural regeneration and repair. A set number of excitatory and inhibitory motor neurons innervate all the limb musculature throughout the normal development and regeneration of a limb. The cell bodies of the motor neurons reside within the segmental ganglion and, upon loss of the limb, their axons regrow from their severed distal ends. The cell bodies of the sensory neurons, in contrast, are located close to their sensory endings within the limb, and they are therefore lost, along with the limb, upon autotomy, leaving the severed, distal axonal stumps of the sensory neurons within the ganglionic root. During the regeneration of a limb, new sensory neurons develop within the limb, and their axons must then grow into the ganglionic root to make the appropriate connections for the new limb to become functional. Evidence is presented in the present paper that the sensory axonal stumps do not degenerate before the new sensory neurons appear within the root as the limb regenerates. These results also indicate a progressive advance of growth cones, presumably sensory in origin, towards the neuropil within the ganglion over time.

Connections between thoraco-coxal proprioceptive afferents and motor neurons in the locust

2000 ◽  
Vol 203 (3) ◽  
pp. 435-445
Author(s):  
M. Wildman
Keyword(s):  
Electrical Stimulation ◽  
Sensory Neurons ◽  
Motor Neurons ◽  
Chordotonal Organ ◽  
Synaptic Connections ◽  
Afferent Neurons ◽  
Postsynaptic Potentials ◽  
The Common ◽  
Proprioceptive Afferents ◽  
Stimulation Of

The position of the coxal segment of the locust hind leg relative to the thorax is monitored by a variety of proprioceptors, including three chordotonal organs and a myochordotonal organ. The sensory neurons of two of these proprioceptors, the posterior joint chordotonal organ (pjCO) and the myochordotonal organ (MCO), have axons in the purely sensory metathoracic nerve 2C (N2C). The connections made by these afferents with metathoracic motor neurons innervating thoraco-coxal and wing muscles were investigated by electrical stimulation of N2C and by matching postsynaptic potentials in motor neurons with afferent spikes in N2C. Stretch applied to the anterior rotator muscle of the coxa (M121), with which the MCO is associated, evoked sensory spikes in N2C. Some of the MCO afferent neurons make direct excitatory chemical synaptic connections with motor neurons innervating the thoraco-coxal muscles M121, M126 and M125. Parallel polysynaptic pathways via unidentified interneurons also exist between MCO afferents and these motor neurons. Connections with the common inhibitor 1 neuron and motor neurons innervating the thoraco-coxal muscles M123/4 and wing muscles M113 and M127 are polysynaptic. Afferents of the pjCO also make polysynaptic connections with motor neurons innervating thoraco-coxal and wing muscles, but no evidence for monosynaptic pathways was found.

The role of interneurons in controlling the tail-withdrawal reflex in Aplysia: a network model

1993 ◽  
Vol 70 (5) ◽  
pp. 1777-1786 ◽  
Author(s):  
J. A. White ◽  
I. Ziv ◽  
L. J. Cleary ◽  
D. A. Baxter ◽  
J. H. Byrne
Keyword(s):  
Synaptic Plasticity ◽  
Sensory Neurons ◽  
Network Model ◽  
Motor Neurons ◽  
Excitatory Postsynaptic Potential ◽  
Layer Model ◽  
Neural Network Models ◽  
Plastic Properties ◽  
Withdrawal Reflex ◽  
Long Duration

1. The contributions of monosynaptic and polysynaptic circuitry to the tail-withdrawal reflex in the marine mollusk Aplysia californica were assessed by the use of physiologically based neural network models. Effects of monosynaptic circuitry were examined by the use of a two-layer network model with four sensory neurons in the input layer and one motor neuron in the output layer. Results of these simulations indicated that the monosynaptic circuit could not account fully for long-duration responses of tail motor neurons elicited by tail stimulation. 2. A three-layer network model was constructed by interposing a layer of two excitatory interneurons between the input and output layers of the two-layer network model. These interneurons had properties mimicking those of the recently described interneuron LP117, receiving excitatory input from pleural sensory neurons and evoking a biphasic excitatory postsynaptic potential (EPSP) in pedal motor neurons (Cleary and Byrne 1993). The three-layer model could account for long-duration responses in motor neurons. 3. Sensory neurons are a known site of plasticity in Aplysia. Synaptic plasticity was incorporated into the three-layer model by altering the magnitudes of conductance changes evoked in motor neurons and interneurons by presynaptic sensory neurons. In these simulations the excitatory interneurons converted an amplitude-coded input into an amplitude- and duration-coded output, allowing the three-layer network to support a large range of output amplitudes and durations. 4. Synaptic plasticity at more than one locus modified dramatically the input-output relationship of the three-layer network model. This feature gave the model redundancy in its plastic properties and points to the possibility of distributed memory in the circuitry mediating withdrawal reflexes in Aplysia. Multiple sites of control over the response of the network would likely allow a more diverse repertoire of responses.

Zebrafish semaphorin Z1a collapses specific growth cones and alters their pathway in vivo

Development ◽  
1998 ◽  
Vol 125 (7) ◽  
pp. 1275-1283 ◽  
Author(s):  
W. Shoji ◽  
C.S. Yee ◽  
J.Y. Kuwada
Keyword(s):  
Sensory Neurons ◽  
Lateral Line ◽  
Knockout Mice ◽  
Specific Growth ◽  
Transmembrane Proteins ◽  
Growth Cones ◽  
In Vitro Activity ◽  
Different Strains

The semaphorin/collapsin gene family encodes secreted and transmembrane proteins several of which can repulse growth cones. Although the in vitro activity of Semaphorin III/D/Collapsin 1 is clear, recent analyses of two different strains of semaphorin III/D/collapsin 1 knockout mice have generated conflicting findings. In order to clarify the in vivo action of this molecule, we analyzed sema Z1a, a zebrafish homolog of semaphorin III/D/collapsin 1. The expression pattern of sema Z1a suggested that it delimited the pathway of the growth cones of a specific set of sensory neurons, the posterior ganglion of the lateral line, in zebrafish. To examine the in vivo action of this molecule, we analyzed (1) the pathways followed by lateral line growth cones in mutants in which the expression of sema Z1a is altered in an interesting way, (2) response of lateral line growth cones to exogenous Sema Z1a in living embryos, and (3) the pathway followed by lateral line growth cones when Sema Z1a is misexpressed by cells along their normal route. The results suggest that a repulsive action of Sema Z1a helps guide the growth cones of the lateral line along their normal pathway.

Sensitization of the gill and siphon withdrawal reflex of Aplysia: multiple sites of change in the neuronal network

1993 ◽  
Vol 70 (3) ◽  
pp. 1210-1220 ◽  
Author(s):  
L. E. Trudeau ◽  
V. F. Castellucci
Keyword(s):  
Sensory Neuron ◽  
Sensory Neurons ◽  
Motor Neurons ◽  
Neuronal Network ◽  
Feedback Inhibition ◽  
Excitatory Input ◽  
Major Mechanism ◽  
Withdrawal Reflex ◽  
The Difference ◽  
Central Synapses

1. Recent studies have emphasized the major contribution of interneuronal transmission to the mediation and learning-associated modulation of the gill and siphon withdrawal (GSW) reflex of Aplysia. We wish to provide more direct support for the hypothesis that inhibitory junctions are crucial sites of plasticity. 2. In parallel experiments we investigated modulation at five major sites of synaptic transmission in the GSW network: 1) from sensory neurons to motor neurons, 2) from sensory neurons to excitatory interneurons (INTs+) 3) from INTs+ to motor neurons (MNs), 4) from inhibitory interneurons (INTs-) to INTs+, and 5) from INTs+ to INTs-. 3. While recording simultaneously from a single sensory neuron of the LE cluster, an INT+, and a MN, we found that both LE-MN and LE-INTs+ synapses were facilitated by the activation of modulator neurons by stimulation of the left pleuroabdominal connective (185 and 93%, respectively) as well as by serotonin (5-HT) (191 and 84%). Junctions of the second type were therefore less facilitated. The difference in the magnitude of facilitation at these two sites is an indication of a branch-specific, differential efficacy in the modulation of different central synapses made by a single neuron. 4. Although INT(+)-MN junctions have the capacity to display marked posttetanic potentiation, they are not significantly potentiated after connective stimulation. Sensitization of the GSW reflex is therefore not necessarily accompanied by a modification of transmission at these synapses. 5. Inhibitory transmission to INTs+ is significantly reduced by connective stimulation (36%) and by 5-HT (71%). This supports the hypothesis that a reduction of feedback inhibition into INTs+ is a major mechanism of reflex sensitization and may account for the increased evoked firing of INTs+ that is observed after connective stimulation. 6. The excitatory input to INTs- is selectively decreased by 5-HT (50%) and by the molluscan neuropeptide small cardioactive peptide B (38%). This latter effect, which could produce disinhibition of INTs+, may explain the previous observation that this peptide is able to potentiate the evoked input to MNs of the reflex at a concentration (1 microM) that fails to modify monosynaptic sensory-motor transmission. 7. These results indicate that transmission through a small neuronal network that mediates a withdrawal reflex in Aplysia may be modulated at multiple sites and by different mechanisms. These mechanisms include: 1) branch-specific facilitation of sensory neuron outputs and 2) inhibition of INT(-)-INT+ inhibitory postsynaptic potentials by endogenous modulatory neurons and by 5-HT.(ABSTRACT TRUNCATED AT 400 WORDS)

scholarly journals Acid-sensing ion channels in sensory signaling

2020 ◽  
Vol 318 (3) ◽  
pp. F531-F543 ◽  
Author(s):  
Marcelo D. Carattino ◽  
Nicolas Montalbetti
Keyword(s):  
Nervous System ◽  
Ion Channels ◽  
Peripheral Nervous System ◽  
Sensory Neurons ◽  
Genetically Modified ◽  
Physiological Processes ◽  
Acid Sensing Ion Channels ◽  
Genetically Modified Mice ◽  
Sensory Processes

Acid-sensing ion channels (ASICs) are cation-permeable channels that in the periphery are primarily expressed in sensory neurons that innervate tissues and organs. Soon after the cloning of the ASIC subunits, almost 20 yr ago, investigators began to use genetically modified mice to assess the role of these channels in physiological processes. These studies provide critical insights about the participation of ASICs in sensory processes, including mechanotransduction, chemoreception, and nociception. Here, we provide an extensive assessment of these findings and discuss the current gaps in knowledge with regard to the functions of ASICs in the peripheral nervous system.

Differential Innervation of Tissues Located at Traditional Acupuncture Points in the Rat Forehead and Face

2018 ◽  
Vol 36 (6) ◽  
pp. 408-414 ◽  
Author(s):  
Jia Wang ◽  
Jingjing Cui ◽  
Chen She ◽  
Dongsheng Xu ◽  
Zhiyun Zhang ◽  
...  
Keyword(s):  
Nervous System ◽  
Sensory Neurons ◽  
Motor Neurons ◽  
Acupuncture Point ◽  
Acupuncture Points ◽  
Motor Nucleus ◽  
Neural Pathways ◽  
Trigeminal Motor Nucleus ◽  
Facial Motor Nucleus ◽  
Neural Tracing

Objectives To compare the neural pathways associated with the tissues located at different traditional acupuncture points in the rat forehead and face using the cholera toxin B subunit (CTB) neural tracing technique. Methods After injection of CTB into the tissues at GB14, ST2 and ST6 in the rat, the neural labelling associated with each acupuncture point was revealed by fluorescent immunohistochemistry of the nervous system, including the trigeminal ganglion (TRG), cervical dorsal root ganglia (DRG), spinal cord and brain. Results The CTB labelling included sensory neurons and their transganglionic axonal terminals, as well as motor neurons. The labelled sensory neurons associated with GB14, ST2 and ST6 were distributed in both the TRG and cervical DRG, and their centrally projected axons terminated in an orderly fashion at their corresponding targets in the spinal trigeminal nucleus and cervical spinal dorsal horn. In addition, labelled motor neurons were observed in the facial motor nucleus, trigeminal motor nucleus and cervical spinal ventral horn, in which facial motor neurons projected to the tissues located at all three acupuncture points. Trigeminal motor neurons innervated both ST2 and ST6, while spinal motor neurons only correlated with ST6. Conclusions These results indicate that the tissues located at each of these three traditional acupuncture points in the rat forehead and face has its own sensory and motor connection with the nervous system in a region-specific pattern through distinct neural pathways. Understanding the neuroanatomical characteristics of acupuncture points from the peripheral nervous system to the central nervous system should help inform acupuncture point selection according to the demands of the clinical situation.

Afferent-Induced Changes in Rhythmic Motor Programs in the Feeding Circuitry of Aplysia

2004 ◽  
Vol 92 (4) ◽  
pp. 2312-2322 ◽  
Author(s):  
Avniel N. Shetreat-Klein ◽  
Elizabeth C. Cropper
Keyword(s):  
Sensory Neurons ◽  
Motor Neurons ◽  
Rhythmic Activity ◽  
Motor Program ◽  
Firing Frequency ◽  
Afferent Activity ◽  
Motor Programs ◽  
Rhythmic Motor ◽  
Induced Changes ◽  
The Impact

A manipulation often used to determine whether a neuron plays a role in the generation of a motor program involves injecting current into the cell during rhythmic activity to determine whether activity is modified. We perform this type of manipulation to study the impact of afferent activity on feeding-like motor programs in Aplysia. We trigger biting-like programs and manipulate sensory neurons that have been implicated in producing the changes in activity that occur when food is ingested, i.e., when bites are converted to bite-swallows. Sensory neurons that are manipulated are the radula mechanoafferent B21 and the retraction proprioceptor B51. Data suggest that both cells are peripherally activated during radula closing/retraction when food is ingested. We found that phasic subthreshold depolarization of a single sensory neuron can significantly prolong radula closing/retraction, as determined by recording both from interneurons (e.g., B64), and motor neurons (e.g., B15 and B8). Additionally, afferent activity produces a delay in the onset of the subsequent radula opening/protraction, and increases the firing frequency of motor neurons. These are the changes in activity that are seen when food is ingested. These results add to the growing data that implicate B21 and B51 in bite to bite-swallow conversions and indicate that afferent activity is important during feeding in Aplysia.

scholarly journals Synergistic integration of Netrin and ephrin axon guidance signals by spinal motor neurons

eLife ◽  
2015 ◽  
Vol 4 ◽  
Author(s):  
Sebastian Poliak ◽  
Daniel Morales ◽  
Louis-Philippe Croteau ◽  
Dayana Krawchuk ◽  
Elena Palmesino ◽  
...  
Keyword(s):  
Motor Neurons ◽  
Molecular Mechanisms ◽  
Neural Circuit ◽  
Growth Cones ◽  
In Vitro Assays ◽  
Dependent Manner ◽  
Motor Axons ◽  
Spinal Motor Neurons ◽  
Spinal Motor

During neural circuit assembly, axonal growth cones are exposed to multiple guidance signals at trajectory choice points. While axonal responses to individual guidance cues have been extensively studied, less is known about responses to combination of signals and underlying molecular mechanisms. Here, we studied the convergence of signals directing trajectory selection of spinal motor axons entering the limb. We first demonstrate that Netrin-1 attracts and repels distinct motor axon populations, according to their expression of Netrin receptors. Quantitative in vitro assays demonstrate that motor axons synergistically integrate both attractive or repulsive Netrin-1 signals together with repulsive ephrin signals. Our investigations of the mechanism of ephrin-B2 and Netrin-1 integration demonstrate that the Netrin receptor Unc5c and the ephrin receptor EphB2 can form a complex in a ligand-dependent manner and that Netrin–ephrin synergistic growth cones responses involve the potentiation of Src family kinase signaling, a common effector of both pathways.

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