POSTSYNAPTIC EFFECTS OF HC-3 AT THE NEUROMUSCULAR JUNCTION OF THE FROG

1961 ◽  
Vol 39 (2) ◽  
pp. 343-349 ◽  
Author(s):  
A. R. Martin ◽  
R. K. Orkand
Keyword(s):  
Neuromuscular Junction ◽  
Intracellular Recording ◽  
Neuromuscular Transmission ◽  
Muscle Fibers ◽  
Marked Change ◽  
Single Muscle ◽  
End Plate ◽  
Quantum Content ◽  
Iontophoretic Application

Intracellular recording from single muscle fibers has been used to study the effects of hemicholinium No. 3 (HC-3) on neuromuscular transmission in the excised m. ext. l. dig. IV of the frog. Concentrations of HC-3 greater than 10−5 M decreased the amplitude of the end-plate potentials (e.p.p.'s) and the magnitude of the depolarization produced by iontophoretic application of acetylcholine. Neither a decrease in e.p.p. quantum content nor depolarization of the end plate accompanied the decreased e.p.p. amplitude. The duration of the potential produced by the application of ACh was increased and the falling phase of the e.p.p. prolonged. 10−4 M HC-3 produced a marked change in the shape of the e.p.p., the effect being similar to that produced by procaine.

Effect of Cooling on Neuromuscular Transmission in the Frog

1958 ◽  
Vol 192 (3) ◽  
pp. 464-470 ◽  
Author(s):  
Choh-Luh Li ◽  
Peter Gouras
Keyword(s):  
Critical Temperature ◽  
Neuromuscular Junction ◽  
Nerve Stimulation ◽  
Neuromuscular Transmission ◽  
The Other ◽  
Sartorius Muscle ◽  
Single Muscle ◽  
Miniature Endplate Potentials ◽  
Endplate Potentials ◽  
Muscle Responses

Recording with intracellular electrodes from endplate regions of frogs sartorius muscle showed that at –1°C miniature endplate potentials still occurred and that the resting membrane potentials differed very little from those recorded at room temperatures. The miniature potentials, however, were decreased in frequency and increased in amplitude by cooling; and at about 5°C, the amplitude began to fall while the frequency continued to be low. It was also at about 5°C that the muscle responses to nerve stimulation frequently consisted of endplate potentials only. Upon rewarming spike potentials again appeared. These observations suggest that there is a critical temperature for neuromuscular transmission, below which impediment of impulse transmission began; and in the frog it is 5°C. The experiments also demonstrated that during the process of cooling a blockage of impulses at one neuromuscular junction and transmission across the other in a single muscle fiber could occur.

Neuromuscular transmission in dystrophic mice

1977 ◽  
Vol 40 (4) ◽  
pp. 836-843 ◽  
Author(s):  
S. Carbonetto
Keyword(s):  
Neuromuscular Transmission ◽  
Neuromuscular Junctions ◽  
Large Population ◽  
Muscle Fibers ◽  
Dystrophic Muscle ◽  
Quantum Content ◽  
Quantal Size ◽  
Significant Difference ◽  
Release Of Acetylcholine ◽  
Dystrophic Mice

1. Neuromuscular transmission was studied in the extensor digitorum-longus muscle of dystrophic mice (strain 129/ReJ) by means of intracellular recording techniques. 2. In a large population of normal and dystrophic muscle fibers tested, the incidence of transmission failure was about 2% and showed no significant difference between the two groups. 3. Quantal size and quantum content of dystrophic junctions were found to be normal. This was true even of nerve terminal on apparently atrophied muscle fibers. 4. The facilitation ratio at dystrophic junctions was not significantly different from normal. 5. Dystrophic neuromuscular junctions exhibited an abnormality high frequency of giant spontaneous potentials. Application of tetrodotoxin (10(-6) M) and curare (10(-6) M) indicated that these potentials were caused by impulse-independent release of acetylcholine. 6. Neuromuscular transmission in dystrophic mice was found functionally normal and unrelated to the degenerative state of the muscle.

The action of sodium pump inhibitors on neuromuscular transmission

1968 ◽  
Vol 170 (1021) ◽  
pp. 381-399 ◽  
Keyword(s):  
Action Potentials ◽  
Neuromuscular Transmission ◽  
Sodium Pump ◽  
Motor Nerve ◽  
Conduction Block ◽  
Progressive Increase ◽  
Frog Skeletal Muscle ◽  
End Plate ◽  
Quantum Content ◽  
Potential Frequency

Exposure of isolated frog skeletal muscle to a cardiac glycoside produces changes in the prejunctional events associated with neuromuscular transmission. The principal changes consist of a progressive increase in the quantum content of the end-plate potential, followed by conduction block in intramuscular motor nerve branches. These events are accompanied by a progressive increase in the frequency of miniature end-plate potentials. Following conduction blockade spontaneous end-plate potentials occur which arise from the generation of action potentials at or near the nerve terminations. Still later, the miniature end-plate potential frequency declines and the nerve endings become entirely inexcitable. These changes appear to result from inhibition of a sodium pump in the motor nerve axons and their endings.

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.

Age-associated changes in neuromuscular transmission in the rat

1984 ◽  
Vol 247 (3) ◽  
pp. C288-C292 ◽  
Author(s):  
D. F. Wilson ◽  
R. C. Cardaman
Keyword(s):  
Neuromuscular Junction ◽  
Action Potentials ◽  
Neuromuscular Transmission ◽  
Age Groups ◽  
Physiological Changes ◽  
Muscle Action ◽  
Rat Diaphragm ◽  
Statistical Probability ◽  
End Plate ◽  
Old Rats

The physiological changes in neuromuscular transmission associated with age were examined in rats between the ages of 1 mo (28 days) and 1 yr (364 days). Intracellular recording techniques were used to monitor end-plate potentials and miniature end-plate potentials at the rat diaphragm neuromuscular junction. Muscle action potentials were blocked by cutting the muscle fibers. Neuromuscular transmission was significantly different in 28-day-old rats compared with the older rats (42-364 days). The 28-day-old rats released fewer quanta. The statistical store in the immature rats was also significantly smaller than in the older age groups. The statistical probability of release, however, was not significantly different from the older animals. Examination of the presynaptic parameters in rats between the ages of 42 and 364 days revealed no significant increases in quantal release. It is concluded that the neuromuscular junction matures physiologically by 6 wk of age in rats and remains stable through the 1st yr of life.

Single Fiber Electromyography

2016 ◽  
pp. 465-483
Author(s):  
Brian A. Crum ◽  
C. Michel Harper
Keyword(s):  
Neuromuscular Junction ◽  
Neuromuscular Transmission ◽  
Muscle Fibers ◽  
Single Fiber ◽  
Recording Equipment ◽  
Fiber Density ◽  
Individual Muscle ◽  
Technical Factors ◽  
Normal Fiber

Single fiber electromyography (SFEMG) is an advanced neurophysiological technique that is primarily used to assess the neuromuscular junction and disorders impairing adequate neuromuscular transmission. SFEMG measurements that are most useful clinically include jitter and blocking, which are quantitative and sensitive measures of neuromuscular transmission inefficiency; and abnormalities in these occur early in the course of diseases, often when standard electrodiagnostic studies are normal. Fiber density assesses the density of individual muscle fibers in each region of the muscle and is increased in a nonspecific manner in most neurogenic and myopathic disorders. SFEMG requires specialized recording equipment, which is used in the collection, display, analysis, reporting, and archiving of SFEMG data. Knowledge of technical limitations and potential pitfalls is vital in acquisition and analysis of SFEMG data. This chapter will review the concepts, methods, measurements, and technical factors related to single fiber EMG. SFEMG findings in various diseases will be reviewed.

Action of Tetraethylammonium Chloride on Neuromuscular Transmission in Frogs

1958 ◽  
Vol 193 (1) ◽  
pp. 213-218 ◽  
Author(s):  
Kyozo Koketsu
Keyword(s):  
Action Potential ◽  
Neuromuscular Transmission ◽  
Direct Action ◽  
Motor Nerve ◽  
Muscle Fibers ◽  
Nerve Fibers ◽  
Tetraethylammonium Chloride ◽  
Nerve Axon ◽  
Mechanical Responses ◽  
End Plate

The action of tetraethylammonium chloride (TEA-Cl) on the neuromuscular transmission in frogs of 0.2–3 mm concentration was analyzed by recording a) the mechanical responses; b) direct action on the muscle fibers; c) end-plate potential (e.p.p.); d) direct action on the end-plate membrane; e) sensitivity of end-plate membrane to the applied ACh; f) the action potential of terminal endings of motor nerve fibers; g) direct action of nerve axon. TEA-Cl in these concentrations augments the e.p.p., and this augmentation increases with increasing concentrations. A relatively higher concentration (1–3 mm) depresses the e.p.p. after an initial augmentation. The sensitivity of the end-plate membrane to ACh is depressed by 0.2–3 mm. TEA-Cl in these concentrations acts on the terminal endings of motor nerve fibers and prolongs the negative after-potential of terminal endings. It is suggested that TEA-Cl increases the release of ACh by acting on the terminal endings, thus causing the augmentation of e.p.p.'s. The action of TEA-Cl at a given concentration will be determined by separate actions both on the end-plate membrane and the terminal ending of motor nerve fibers.

Contractile inactivation in frog single denervated muscle fibers

1975 ◽  
Vol 229 (6) ◽  
pp. 1492-1497 ◽  
Author(s):  
SC Stuesse ◽  
BD Lindley
Keyword(s):  
Neuromuscular Transmission ◽  
Calcium Concentration ◽  
External Medium ◽  
Fiber Diameter ◽  
Muscle Fibers ◽  
Ringer Solution ◽  
Single Muscle ◽  
Denervated Muscle ◽  
Do Control

After preliminary conditioning depolarizations, single muscle fibers of the frog were tested for ability to contract in response to depolarization by 100 mM K+ Ringer solution. Denervated fibers (6-42 days) lose their ability to produce a 100 mM K+ contracture more rapidly than do control fibers. This decrease in 100 mM K+ contracture size (inactivation) is dependent on length of exposure to and magnitude of the conditioning depolarization and on the calcium concentration in the external medium. At 0.4 mM Ca++, the inactivation is 3 times faster than at 1.5 mM Ca++. The rate of contracture loss is not correlated with fiber diameter or the number of days after failure of neuromuscular transmission, and the preliminary conditioning depolarizations do not affect the rate of terminal relaxation from the 100 mM K+ contractures.

scholarly journals Near-Fibre Electromyography

2020 ◽  
Author(s):  
Mathew Piasecki ◽  
Oscar Garnés C. Estruch ◽  
Daniel W Stashuk
Keyword(s):  
Neuromuscular Junction ◽  
Motor Unit ◽  
Neuromuscular Transmission ◽  
Neuromuscular Disorders ◽  
Fibre Diameter ◽  
Time Variability ◽  
Motor Unit Potential ◽  
Muscle Recruitment ◽  
End Plate ◽  
High Pass

AbstractNear fibre electromyography (NFEMG) is the use of specifically high-pass filtered motor unit potential (MUPs) (i.e. near fibre MUPs (NFMs)) extracted from needle-detected EMG signals for the examination of changes in motor unit (MU) morphology and electrophysiology caused by neuromuscular disorders or ageing. The concepts of NFEMG, the parameters used, including NFM duration and dispersion, which relates to fibre diameter variability and/or endplate scatter, and a new measure of neuromuscular junction transmission (NMJ) instability, NFM segment jitter, and the methods for obtaining their values are explained. Evaluations using simulated needle-detected EMG data and exemplary human data are presented, described and discussed. The data presented demonstrate the ability of using NFEMG parameters to detect changes in MU fibre diameter variability, end plate scatter, and neuromuscular transmission time variability. These changes can be detected prior to alterations of MU size, numbers or muscle recruitment patterns.

scholarly journals Presynaptic Paraneoplastic Disorders of the Neuromuscular Junction: An Update

2021 ◽  
Vol 11 (8) ◽  
pp. 1035
Author(s):  
Maria Pia Giannoccaro ◽  
Patrizia Avoni ◽  
Rocco Liguori
Keyword(s):  
Potassium Channels ◽  
Neuromuscular Junction ◽  
Calcium Channels ◽  
Myasthenia Gravis ◽  
Neuromuscular Transmission ◽  
Voltage Gated ◽  
Voltage Gated Calcium Channels ◽  
Immune Mediated ◽  
Recent Developments ◽  
Myasthenic Syndrome

The neuromuscular junction (NMJ) is the target of a variety of immune-mediated disorders, usually classified as presynaptic and postsynaptic, according to the site of the antigenic target and consequently of the neuromuscular transmission alteration. Although less common than the classical autoimmune postsynaptic myasthenia gravis, presynaptic disorders are important to recognize due to the frequent association with cancer. Lambert Eaton myasthenic syndrome is due to a presynaptic failure to release acetylcholine, caused by antibodies to the presynaptic voltage-gated calcium channels. Acquired neuromyotonia is a condition characterized by nerve hyperexcitability often due to the presence of antibodies against proteins associated with voltage-gated potassium channels. This review will focus on the recent developments in the autoimmune presynaptic disorders of the NMJ.

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