Neuromuscular Junction (NMJ): Activity-Dependent Muscle Fiber Modulation

2009 ◽  
pp. 559-568 ◽  
Author(s):  
T. Lømo
Keyword(s):  
Neuromuscular Junction ◽  
Muscle Fiber ◽  
Activity Dependent

Vitamin D and/or calcium deficient diets may differentially affect muscle fiber neuromuscular junction innervation

2016 ◽  
Vol 54 (6) ◽  
pp. 1120-1132 ◽  
Author(s):  
David J. Gifondorwa ◽  
Tyran D. Thompson ◽  
June Wiley ◽  
Alexander E. Culver ◽  
Pamela K. Shetler ◽  
...  
Keyword(s):  
Vitamin D ◽  
Neuromuscular Junction ◽  
Muscle Fiber

scholarly journals Effects of Vocal Training on Thyroarytenoid Muscle Neuromuscular Junctions and Myofibers in Young and Older Rats

2020 ◽  
Author(s):  
Adrianna C Shembel ◽  
Charles Lenell ◽  
Sophia Chen ◽  
Aaron M Johnson
Keyword(s):  
Neuromuscular Junction ◽  
Muscle Fiber ◽  
Acoustic Analysis ◽  
Neuromuscular Junctions ◽  
Fiber Type ◽  
Male Rats ◽  
Brown Norway ◽  
Control Group ◽  
Vocal Training ◽  
Thyroarytenoid Muscle

Abstract The purpose of this investigation was to determine the effects of vocal training on neuromuscular junction (NMJ) morphology and muscle fiber size and composition in the thyroarytenoid muscle, the primary muscle in the vocal fold, in younger (9-month) and older (24-month) Fischer 344 × Brown Norway male rats. Over 4 or 8 weeks of vocal training, rats of both ages progressively increased their daily number of ultrasonic vocalizations (USVs) through operant conditioning and were then compared to an untrained control group. Neuromuscular junction morphology and myofiber size and composition were measured from the thyroarytenoid muscle. Acoustic analysis of USVs before and after training quantified the functional effect of training. Both 4- and 8-week training resulted in less NMJ motor endplate dispersion in the lateral portion of the thyroarytenoid muscle in rats of both ages. Vocal training and age had no significant effects on laryngeal myofiber size or type. Vocal training resulted in a greater number of USVs with longer duration and increased intensity. This study demonstrated that vocal training induces laryngeal NMJ morphology and acoustic changes. The lack of significant effects of vocal training on muscle fiber type and size suggests vocal training significantly improves neuromuscular efficiency but does not significantly influence muscle strength changes.

scholarly journals Glutamate at the Vertebrate Neuromuscular Junction: From Modulation to Neurotransmission

Cells ◽  
2019 ◽  
Vol 8 (9) ◽  
pp. 996 ◽  
Author(s):  
Colombo ◽  
Francolini
Keyword(s):  
Neuromuscular Junction ◽  
Signaling Pathways ◽  
Muscle Fiber ◽  
Neuromuscular Junctions ◽  
Motor Nerve ◽  
Vertebrate Development ◽  
Motor Nerve Ending ◽  
Downstream Signaling ◽  
Synaptic Neurotransmission ◽  
Synaptic Receptors

Although acetylcholine is the major neurotransmitter operating at the skeletal neuromuscular junction of many invertebrates and of vertebrates, glutamate participates in modulating cholinergic transmission and plastic changes in the last. Presynaptic terminals of neuromuscular junctions contain and release glutamate that contribute to the regulation of synaptic neurotransmission through its interaction with pre- and post-synaptic receptors activating downstream signaling pathways that tune synaptic efficacy and plasticity. During vertebrate development, the chemical nature of the neurotransmitter at the vertebrate neuromuscular junction can be experimentally shifted from acetylcholine to other mediators (including glutamate) through the modulation of calcium dynamics in motoneurons and, when the neurotransmitter changes, the muscle fiber expresses and assembles new receptors to match the nature of the new mediator. Finally, in adult rodents, by diverting descending spinal glutamatergic axons to a denervated muscle, a functional reinnervation can be achieved with the formation of new neuromuscular junctions that use glutamate as neurotransmitter and express ionotropic glutamate receptors and other markers of central glutamatergic synapses. Here, we summarize the past and recent experimental evidences in support of a role of glutamate as a mediator at the synapse between the motor nerve ending and the skeletal muscle fiber, focusing on the molecules and signaling pathways that are present and activated by glutamate at the vertebrate neuromuscular junction.

scholarly journals Opposed Actions of PKA Isozymes (RI and RII) and PKC Isoforms (cPKCβI and nPKCε) in Neuromuscular Developmental Synapse Elimination

Cells ◽  
2019 ◽  
Vol 8 (11) ◽  
pp. 1304
Author(s):  
Garcia ◽  
Balañà ◽  
Lanuza ◽  
Tomàs ◽  
Cilleros-Mañé ◽  
...  
Keyword(s):  
Neuromuscular Junction ◽  
Protein Kinases ◽  
Presynaptic Receptors ◽  
Axonal Loss ◽  
Synapse Elimination ◽  
Cluster Morphology ◽  
Pkc Isoforms ◽  
Receptor Action ◽  
Induced Changes ◽  
Activity Dependent

Background: During neuromuscular junction (NMJ) development, synapses are produced in excess. By sensing the activity-dependent release of ACh, adenosine, and neurotrophins, presynaptic receptors prompt axonal competition and loss of the unnecessary axons. The receptor action is mediated by synergistic and antagonistic relations when they couple to downstream kinases (mainly protein kinases A and C (PKA and PKC)), which phosphorylate targets involved in axonal disconnection. Here, we directly investigated the involvement of PKA subunits and PKC isoforms in synapse elimination. Methods: Selective PKA and PKC peptide modulators were applied daily to the Levator auris longus (LAL) muscle surface of P5–P8 transgenic B6.Cg-Tg (Thy1-YFP) 16 Jrs/J (and also C57BL/6J) mice, and the number of axons and the postsynaptic receptor cluster morphology were evaluated in P9 NMJ. Results: PKA (PKA-I and PKA-II isozymes) acts at the pre- and postsynaptic sites to delay both axonal elimination and nAChR cluster differentiation, PKC activity promotes both axonal loss (a cPKCβI and nPKCε isoform action), and postsynaptic nAChR cluster maturation (a possible role for PKCθ). Moreover, PKC-induced changes in axon number indirectly influence postsynaptic maturation. Conclusions: PKC and PKA have opposed actions, which suggests that changes in the balance of these kinases may play a major role in the mechanism of developmental synapse elimination.

Neuromuscular Junction Disorders

2021 ◽  
pp. 772-778
Author(s):  
Brent P. Goodman
Keyword(s):  
Neuromuscular Junction ◽  
Action Potential ◽  
Motor Unit ◽  
Safety Factor ◽  
Muscle Fiber ◽  
Nerve Terminal ◽  
Neuromuscular Transmission ◽  
Critical Component ◽  
End Plate ◽  
Unmyelinated Nerve

The neuromuscular junction (NMJ) is a critical component of the motor unit that is made up of the distal, unmyelinated nerve terminal, synaptic space, and end-plate region of the muscle fiber. Contraction of muscle fiber involves a coordinated series of steps that ultimately generates an action potential at the muscle end plate (also known as an end-plate potential). Normally the end-plate potential substantially exceeds the threshold necessary to trigger an action potential in the muscle fiber, and this difference is termed the safety factor of neuromuscular transmission. Disorders that affect the NMJ reduce this safety factor, a change that results in fatigable weakness.

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