scholarly journals Interactions of the Giant Fibres and Motor Giant Neurones of the Hermit Crab

1987 ◽  
Vol 133 (1) ◽  
pp. 353-370
Author(s):  
W. J. HEITLER ◽  
K. FRASER
Keyword(s):  
Hermit Crab ◽  
Electrical Synapse ◽  
Chemical Synapse ◽  
Electrical Synapses ◽  
Giant Fibre ◽  
Giant Neurone ◽  
Giant Fibres ◽  
Chemical Synapses ◽  
Contralateral Motor ◽  
Recent Claim

A recent claim that the giant fibre of the hermit crab excites its contralateral motor giant neurone through a chemical rather than an electrical synapse (Stephens, 1986) was re-examined. We found that the reported increased latency (relative to the electrical ipsilateral synapse) was postsynaptic in origin, as was the increased spike ‘jitter’. There was no difference in synaptic latency between the electrical synapse and the supposed chemical one. We did not find a consistent resistance to N-ethylmaleimide (an uncoupler of electrical synapses) by the supposed chemical synapse, but the synapse was resistant to 2 mmol 1−1 cadmium, which blocks known chemical synapses in the system. Sub-threshold depolarizing current passed from the presynaptic giant fibre to the postsynaptic contralateral motor giant, and hyperpolarizing current passed antidromically. We conclude that the synapse is electrical and not chemical in nature.

scholarly journals The Segmental Giant Neurone of the Hermit Crab Eupagurus Bernhardus

1986 ◽  
Vol 125 (1) ◽  
pp. 245-269 ◽  
Author(s):  
W. J. Heitler ◽  
K. Fraser
Keyword(s):  
Cell Body ◽  
Hermit Crab ◽  
Small Cell ◽  
Electrical Synapse ◽  
Giant Fibre ◽  
Anatomy And Physiology ◽  
Motor Neurones ◽  
Evolutionary Paths ◽  
Contralateral Motor ◽  
Giant Fibre System

The anatomy and physiology of the segmental giant (SG) neurone of the fourth abdominal ganglion of the hermit crab is described. The SG has an apparently blindending axon in the first root and a small cell body in the anterior ipsilateral ventral quadrant of the ganglion. There is a large ipsilateral neuropile arborization with prominent dendrites lined up along the course of the ipsilateral giant fibre (GF). The SG receives 1:1 input from the ipsilateral GF via an electrical synapse which is usually rectifying. SG activation produces a large EPSP in all ipsilateral and some contralateral fast flexor excitor (FF) motor neurones. The major input to FFs resulting from GF activation appears to be mediated via the SG. It also produces a small EPSP in ipsilateral and contralateral motor giant neurones. The properties of the hermit crab SG are compared to those of the crayfish SG, and the implications of the SG for the possible evolutionary paths of the giant fibre system are discussed.

scholarly journals Asymmetry of an intracellular scaffold at vertebrate electrical synapses

2017 ◽  
Author(s):  
Audrey J Marsh ◽  
Jennifer Carlisle Michel ◽  
Anisha P Adke ◽  
Emily L Heckman ◽  
Adam C Miller
Keyword(s):  
Gap Junction ◽  
Synapse Formation ◽  
Neural Circuit ◽  
Electrical Synapse ◽  
Electrical Synapses ◽  
Gap Junction Channels ◽  
Junction Protein ◽  
Chemical Synapses ◽  
And Function

AbstractNeuronal synaptic connections are electrical or chemical and together are essential to dynamically defining neural circuit function. While chemical synapses are well known for their biochemical complexity, electrical synapses are often viewed as comprised solely of neuronal gap junction channels that allow direct ionic and metabolic communication. However, associated with the gap junction channels are structures observed by electron microscopy called the Electrical Synapse Density (ESD). The ESD has been suggested to be critical for the formation and function of the electrical synapse, yet the biochemical makeup of these structures is poorly understood. Here we find that electrical synapse formation in vivo requires an intracellular scaffold called Tight Junction Protein 1b (Tjp1b). Tjp1b is localized to electrical synapses where it is required for the stabilization of the gap junction channels and for electrical synapse function. Strikingly, we find that Tjp1b protein localizes and functions asymmetrically, exclusively on the postsynaptic side of the synapse. Our findings support a novel model in which there is molecular asymmetry at the level of the intracellular scaffold that is required for building the electrical synapse. ESD molecular asymmetries may be a fundamental motif of all nervous systems and could support functional asymmetry at the electrical synapse.

scholarly journals Theoretical Analysis of Coupled Modified Hindmarsh-rose Model Under Transcranial Magnetic-acoustic Electrical Stimulation

2022 ◽  
Vol 16 ◽  
pp. 610-617
Author(s):  
Liang Guo ◽  
Shuai Zhang ◽  
Jiankang Wu ◽  
Xinyu Gao ◽  
Mingkang Zhao ◽  
...  
Keyword(s):  
Nervous System ◽  
Electrical Stimulation ◽  
Modulation Frequency ◽  
Ultrasonic Waves ◽  
Neuronal Firing ◽  
Electrical Synapse ◽  
Discharge Frequency ◽  
Neural Network Modeling ◽  
Chemical Synapse ◽  
Chemical Synapses

Transcranial magnetic-acoustic electrical stimulation (TMAES) is a new technology with ultrasonic waves and a static magnetic field to generate an electric current in nerve tissues to modulate neuronal firing activities. The existing neuron models only simulate a single neuron, and there are few studies on coupled neurons models about TMAES. Most of the neurons in the cerebral cortex are not isolated but are coupled to each other. It is necessary to study the information transmission of coupled neurons. The types of neuron coupled synapses include electrical synapse and chemical synapse. A neuron model without considering chemical synapses is not comprehensive. Here, we modified the Hindmarsh-Rose (HR) model to simulate the smallest nervous system—two neurons coupled electrical synapses and chemical synapses under TMAES. And the environmental variables describing the synaptic coupling between two neurons and the nonlinearity of the nervous system are also taken into account. The firing behavior of the nervous system can be modulated by changing the intensity or the modulation frequency. The results show that within a certain range of parameters, the discharge frequency of coupled neurons could be increased by altering the modulation frequency, and intensity of stimulation, modulating the excitability of neurons, reducing the response time of chemical postsynaptic neurons, and accelerating the information transferring. Moreover, the discharge frequency of neurons was selective to stimulus parameters. These results demonstrate the possible theoretical regulatory mechanism of the neurons' firing frequency characteristics by TMAES. The study establishes the foundation for large-scale neural network modeling and can be taken as the theoretical basis for TMAES experimental and clinical application.

scholarly journals Extensive GJD2 Expression in the Song Motor Pathway Reveals the Extent of Electrical Synapses in the Songbird Brain

Biology ◽  
2021 ◽  
Vol 10 (11) ◽  
pp. 1099
Author(s):  
Pepe Alcami ◽  
Santhosh Totagera ◽  
Nina Sohnius-Wilhelmi ◽  
Stefan Leitner ◽  
Benedikt Grothe ◽  
...  
Keyword(s):  
Mrna Expression ◽  
Cell Types ◽  
Brain Regions ◽  
Skill Learning ◽  
Electrical Synapse ◽  
Suitable Model ◽  
Sequencing Data ◽  
Electrical Synapses ◽  
Connexin 36 ◽  
Chemical Synapses

Birdsong is a precisely timed animal behavior. The connectivity of song premotor neural networks has been proposed to underlie the temporal patterns of neuronal activity that control vo-cal muscle movements during singing. Although the connectivity of premotor nuclei via chemical synapses has been characterized, electrical synapses and their molecular identity remain unex-plored. We show with in situ hybridizations that GJD2 mRNA, coding for the major channel-form-ing electrical synapse protein in mammals, connexin 36, is expressed in the two nuclei that control song production, HVC and RA from canaries and zebra finches. In canaries’ HVC, GJD2 mRNA is extensively expressed in GABAergic and only a fraction of glutamatergic cells. By contrast, in RA, GJD2 mRNA expression is widespread in glutamatergic and GABAergic neurons. Remarkably, GJD2 expression is similar in song nuclei and their respective embedding brain regions, revealing the widespread expression of GJD2 in the avian brain. Inspection of a single-cell sequencing data-base from zebra and Bengalese finches generalizes the distributions of electrical synapses across cell types and song nuclei that we found in HVC and RA from canaries, reveals a differential GJD2 mRNA expression in HVC glutamatergic subtypes and its transient increase along the neurogenic lineage. We propose that songbirds are a suitable model to investigate the contribution of electrical synapses to motor skill learning and production.

Electrical and Chemical Synapses Between Giant Interneurones and Giant Flexor Motor Neurones of the Hermit Crab (Pagurus Pollicaris)

1986 ◽  
Vol 123 (1) ◽  
pp. 217-228
Author(s):  
PHILIP J. STEPHENS
Keyword(s):  
Hermit Crab ◽  
Synaptic Connection ◽  
Lucifer Yellow ◽  
Electrical Synapse ◽  
Synaptic Delay ◽  
Single Pair ◽  
Lucifer Yellow Ch ◽  
Close Proximity ◽  
Motor Neurones ◽  
Chemical Synapses

1. An examination is made of the characteristics of the synapses between the single pair of giant interneurones (GIs) and the giant flexor motor neurones (GFMNs) in the fused thoracic-abdominal (TA) ganglion of the hermit crab Pagurus pollicaris. 2. There is an electrical synapse between each GI and its ipsilateral GFMN. Evidence for this includes (a) dye (Lucifer Yellow CH) coupling between the two neurones, (b) a short synaptic (0.2 ms) delay between spikes in the two axons, (c) the ability to pass hyperpolarizing current between the two neurones and (d) the sensitivity of the connection to bath applications of N-ethylmaleimide. This synaptic connection is rectifying, since a GFMN spike does not provoke an action potential in the GI. 3. There is a connection between the GI and the contralateral GFMN. Data indicating that this synaptic connection is chemical includes (a) a synaptic delay of between 0.6 and 0.8 ms, (b) transmission i9 easily and irreversibly fatigued, (c) the synapse is insensitive to N-ethylmaleimide and (d) there is no dye coupling between the two neurones. 4. Branches of the GFMN come in close proximity with the GI on both sides of the TA ganglion. However, it is not known whether there is a direct connection or an intervening neurone between the GI and the contralateral GFMN.

THE HISTOLOGY OF THE GIANT FIBRE SYSTEM IN THE ABDOMINAL VENTRAL NERVE CORD OF THE DESERT LOCUST

1970 ◽  
Vol 102 (9) ◽  
pp. 1163-1168 ◽  
Author(s):  
W. D. Seabrook
Keyword(s):  
Single Cell ◽  
Nerve Cord ◽  
Ventral Nerve Cord ◽  
Schistocerca Gregaria ◽  
Desert Locust ◽  
Giant Fibre ◽  
Metathoracic Ganglion ◽  
Giant Fibres ◽  
Giant Fibre System

AbstractSchistocerca gregaria possess four neurones of giant fibre proportions within the abdominal ventral nerve cord. These fibres arise from single cell bodies in the terminal ganglionic mass and pass without interruption to the metathoracic ganglion. Fibres become reduced in diameter when passing through a ganglion. Branching of the giant fibres occurs in abdominal ganglia 6 and 7.

Structure and Function of the Lateral Giant Neurone of the Primitive Crustacean Anaspides Tasmaniae

1979 ◽  
Vol 78 (1) ◽  
pp. 121-136
Author(s):  
GERALD E. SILVEY ◽  
IAN S. WILSON
Keyword(s):  
Action Potentials ◽  
Tactile Stimulation ◽  
Large Diameter ◽  
Whole Body ◽  
Giant Fibre ◽  
Single Action ◽  
Giant Neurone ◽  
And Function ◽  
Thoracic And Abdominal ◽  
Stimulation Of

The syncarid crustacean Anaspides tasmaniae rapidly flexes its free thoracic and abdominal segments in response to tactile stimulation of its body. This response decrements but recovers in slightly more than one hour. The fast flexion is evoked by single action potentials in the lateral of two large diameter fibres (40 μm) which lie on either side of the cord. The lateral giant fibre is made up of fused axons of 11 neurones, one in each of the last 5 thoracic and 6 abdominal ganglia. The soma of each neurone lies contralateral to the axon. Its neurite crosses that of its counterpart in the commissure and gives out dendrites into the neuropile of each hemiganglion. The lateral giant neurone receives input from the whole body but fires in response only to input from the fourth thoracic segment posteriorly. Both fibres respond with tactile stimulation of only one side. Since neither current nor action potentials spread from one fibre to the other, afferents must synapse with both giant neurones. The close morphological and physiological similarities of the lateral giant neurone in Anaspides to that in the crayfish (Eucarida) suggest that the lateral giant system arose in the ancestor common to syncarids and eucarids, prior to the Carboniferous.

Effects of Time Delay on Burst Synchronization Transition of Neuronal Networks

2018 ◽  
Vol 28 (12) ◽  
pp. 1850143 ◽  
Author(s):  
Xiaojuan Sun ◽  
Tianshu Xue
Keyword(s):  
Time Delay ◽  
Neuronal Network ◽  
Coupling Strength ◽  
Neuronal Networks ◽  
The Other ◽  
Electrical Synapses ◽  
Synchronization Transition ◽  
Burst Synchronization ◽  
Chemical Synapses ◽  
Bursting Activity

In this paper, we focus on investigating the effects of time delay on burst synchronization transitions of a neuronal network which is locally modeled by Hindmarsh–Rose neurons. Here, neurons inside the neuronal network are connected through electrical synapses or chemical synapses. With the numerical results, it is revealed that burst synchronization transitions of both electrically and chemically coupled neuronal networks could be induced by time delay just when the coupling strength is large enough. Meanwhile, it is found that, in electrically and excitatory chemically coupled neuronal networks, burst synchronization transitions are observed through change of spiking number per burst when coupling strength is large enough; while in inhibitory chemically coupled neuronal network, burst synchronization transitions are observed for large enough coupling strength through changing fold-Hopf bursting activity to fold-homoclinic bursting activity and vice versa. Namely, two types of burst synchronization transitions are observed. One type of burst synchronization transitions occurs through change of spiking numbers per burst and the other type of burst synchronization transition occurs through change of bursting types.

Meclofenamic Acid Blocks Electrical Synapses of Retinal AII Amacrine and on-Cone Bipolar Cells

2009 ◽  
Vol 101 (5) ◽  
pp. 2339-2347 ◽  
Author(s):  
Margaret Lin Veruki ◽  
Espen Hartveit
Keyword(s):  
Amacrine Cells ◽  
Bipolar Cells ◽  
Electrical Synapse ◽  
Dependent Manner ◽  
Electrical Synapses ◽  
Meclofenamic Acid ◽  
Aii Amacrine Cells ◽  
Rod Pathway ◽  
Aii Amacrine ◽  
Cone Bipolar Cells

Gap junction channels constitute specialized intercellular contacts that can serve as electrical synapses. In the rod pathway of the retina, electrical synapses between AII amacrine cells express connexin 36 (Cx36) and electrical synapses between AII amacrines and on-cone bipolar cells express Cx36 on the amacrine side and Cx36 or Cx45 on the bipolar side. For physiological investigations of the properties and functions of these electrical synapses, it is highly desirable to have access to potent pharmacological blockers with selective and reversible action. Here we use dual whole cell voltage-clamp recordings of pairs of AII amacrine cells and pairs of AII amacrine and on-cone bipolar cells in rat retinal slices to directly measure the junctional conductance ( Gj) between electrically coupled cells and to study the effect of the drug meclofenamic acid (MFA) on Gj. Consistent with previous tracer coupling studies, we found that MFA reversibly blocked the electrical synapse currents in a concentration-dependent manner, with complete block at 100 μM. Whereas MFA evoked a detectable decrease in Gj within minutes of application, the time to complete block of Gj was considerably longer, typically 20–40 min. After washout, Gj recovered to 20–90% of the control level, but the time to maximum recovery was typically >1 h. These results suggest that MFA can be a useful drug to investigate the physiological functions of electrical synapses in the rod pathway, but that the slow kinetics of block and reversal might compromise interpretation of the results and that explicit monitoring of Gj is desirable.

scholarly journals Electrical synaptic transmission requires a postsynaptic scaffolding protein

2020 ◽  
Author(s):  
Abagael M. Lasseigne ◽  
Fabio A. Echeverry ◽  
Sundas Ijaz ◽  
Jennifer Carlisle Michel ◽  
E. Anne Martin ◽  
...  
Keyword(s):  
Synaptic Transmission ◽  
Gap Junctions ◽  
Functional Organization ◽  
Scaffolding Protein ◽  
Scaffolding Proteins ◽  
Electrical Transmission ◽  
Critical Function ◽  
Electrical Synapses ◽  
Intercellular Channels ◽  
Chemical Synapses

SUMMARYElectrical synaptic transmission relies on neuronal gap junctions containing channels constructed by Connexins. While at chemical synapses neurotransmitter-gated ion channels are critically supported by scaffolding proteins, it is unknown if channels at electrical synapses require similar scaffold support. Here we investigated the functional relationship between neuronal Connexins and Zonula Occludens 1 (ZO1), an intracellular scaffolding protein localized to electrical synapses. Using model electrical synapses in zebrafish Mauthner cells, we demonstrated that ZO1 is required for robust synaptic Connexin localization, but Connexins are dispensable for ZO1 localization. Disrupting this hierarchical ZO1/Connexin relationship abolishes electrical transmission and disrupts Mauthner-cell-initiated escape responses. We found that ZO1 is asymmetrically localized exclusively postsynaptically at neuronal contacts where it functions to assemble intercellular channels. Thus, forming functional neuronal gap junctions requires a postsynaptic scaffolding protein. The critical function of a scaffolding molecule reveals an unanticipated complexity of molecular and functional organization at electrical synapses.

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