The quantal release of transmitters at two neuromuscular junctions in the crayfish

1974 ◽  
Vol 91 (2) ◽  
pp. 111-125 ◽  
Author(s):  
William Van der Kloot ◽  
Hiroshi Kita
Keyword(s):  
Neuromuscular Junctions ◽  
Quantal Release

Modulation of the kinetics of evoked quantal release at mouse neuromuscular junctions by calcium and strontium

2007 ◽  
Vol 100 (4) ◽  
pp. 939-949 ◽  
Author(s):  
Ellya A. Bukharaeva ◽  
Dmitry Samigullin ◽  
Eugeny E. Nikolsky ◽  
Lev G. Magazanik
Keyword(s):  
Neuromuscular Junctions ◽  
Quantal Release ◽  
Kinetics Of

Latency of transmitter release at crayfish motor nerve endings examined by intracellular depolarization

1987 ◽  
Vol 65 (1) ◽  
pp. 105-108 ◽  
Author(s):  
J. M. Wojtowicz ◽  
I. Parnas ◽  
H. Parnas ◽  
H. L. Atwood
Keyword(s):  
Transmitter Release ◽  
Sampling Methods ◽  
Procambarus Clarkii ◽  
Neuromuscular Junctions ◽  
Motor Nerve ◽  
Nerve Endings ◽  
Quantal Release ◽  
Moderate Size ◽  
Axon Branch ◽  
Individual Motor

Latency of release of individual quanta of transmitter was studied at neuromuscular junctions of a crayfish (Procambarus clarkii). Postsynaptic quantal currents were recorded at individual motor nerve endings with a macropatch electrode while the subterminal axon branch was depolarized by current passed through an intracellular microelectrode. For depolarizing currents of moderate size, the latency of transmitter release did not change when the duration of the depolarizing current was altered. Previous studies in which a contrary result was obtained may have been compromised by artefacts or by the sampling methods employed. The present results do not support the hypothesis of a depolarization-induced "repressor" of quantal release.

Quantal release and facilitation at frog neuromuscular junctions at about 0 degrees C

1991 ◽  
Vol 65 (4) ◽  
pp. 834-840 ◽  
Author(s):  
J. Molgo ◽  
W. Van der Kloot
Keyword(s):  
Time Course ◽  
Neuromuscular Junctions ◽  
Frog Neuromuscular Junction ◽  
Deconvolution Method ◽  
Release Process ◽  
Quantal Release ◽  
Probabilistic Nature ◽  
Kinetics Of ◽  
Insight Into ◽  
Plate Current

1. It has been reported that at the frog neuromuscular junction at temperatures around 0 degrees C the release of transmitter quanta following nerve stimulation becomes disrupted, and the facilitation obtained after a second stimulus is no longer detectable. We thought that further investigation might give insight into the mechanism of quantal release, so we undertook experiments on Rana pipiens and Rana berlanieri. 2. In these species neuromuscular transmission occurs at temperatures as low as -0.8 degrees C. As the temperature is decreased further, transmission fails, apparently by a block in nerve conduction. The number of quanta released per stimulus decreases as temperature is lowered, with a Q10 of approximately 2.4. Owing to the decrease in the quantal output and the probabilistic nature of the release process, in occasional single records of an end-plate current (EPC), the pattern of release appeared disrupted. The kinetics of quantal release was studied by the use of a deconvolution method, which requires recording of EPCs and miniature EPCs (MEPCs) in preparations in high Mg(2+)-low Ca2+ solution. At approximately 0 degrees C the pattern of quantal release was similar to that at higher temperatures, although with a slower time course. At 0 degrees C the peak of release occurred approximately 3.5 ms after onset. 3. In our experiments there was almost no difference in the frequency of MEPCs at 22 degrees C and at 0 degree C. 4. We observed as much facilitation to a second stimulus at 0 degree C as at 10 degrees C. The Q10 for the decay of facilitation with time was between 1.9 and 2.3.(ABSTRACT TRUNCATED AT 250 WORDS)

Quantal Secretion and Nerve-Terminal Cable Properties at Neuromuscular Junctions in an Amphibian (Bufo marinus)

1999 ◽  
Vol 81 (3) ◽  
pp. 1135-1146 ◽  
Author(s):  
G. T. Macleod ◽  
L. Farnell ◽  
W. G. Gibson ◽  
M. R. Bennett
Keyword(s):  
Nerve Terminal ◽  
Neuromuscular Junctions ◽  
Motor Nerve ◽  
Current Injection ◽  
Bufo Marinus ◽  
Motor Nerve Terminal ◽  
Terminal Branch ◽  
Quantal Release ◽  
Cable Properties ◽  
Test Electrode

Quantal secretion and nerve-terminal cable properties at neuromuscular junctions in an amphibian ( Bufo marinus). The effect of a conditioning depolarizing current pulse (80–200 μs) on quantal secretion evoked by a similar test pulse at another site was examined in visualized motor-nerve terminal branches of amphibian endplates ( Bufo marinus). Tetrodotoxin (200 nM) and cadmium (50 μM) were used to block voltage-dependent sodium and calcium conductances. Quantal release at the test electrode was depressed at different distances (28–135 μm) from the conditioning electrode when the conditioning and test pulses were delivered simultaneously. This depression decreased when the interval between conditioning and test current pulses was increased, until, at an interval of ∼0.25 ms, it was negligible. At no time during several thousand test-conditioning pairs, for electrodes at different distances apart (28–135 μm) on the same or contiguous terminal branches, did the electrotonic effects of quantal release at one electrode produce quantal release at the other. Analytic and numerical solutions were obtained for the distribution of transmembrane potential at different sites along terminal branches of different lengths for current injection at a point on a terminal branch wrapped in Schwann cell, in the absence of active membrane conductances. Solutions were also obtained for the combined effects of two sites of current injection separated by different time delays. This cable model shows that depolarizing current injections of a few hundred microseconds duration produce hyperpolarizations at ∼30 μm beyond the site of current injection, with these becoming larger and occurring at shorter distances the shorter the terminal branch. Thus the effect of a conditioning depolarizing pulse at one site on a subsequent test pulse at another more than ∼30 μm away is to substantially decrease the absolute depolarization produced by the latter, provided the interval between the pulses is less than a few hundred microseconds. It is concluded that the passive cable properties of motor nerve terminal branches are sufficient to explain the effects on quantal secretion by a test electrode depolarization of current injections from a spatially removed conditioning electrode.

scholarly journals Noradrenaline synchronizes evoked quantal release at frog neuromuscular junctions

1999 ◽  
Vol 517 (3) ◽  
pp. 879-888 ◽  
Author(s):  
Ella A. Bukcharaeva ◽  
Kira C. Kim ◽  
J. Moravec ◽  
E. E. Nikolsky ◽  
F. Vyskočil
Keyword(s):  
Neuromuscular Junctions ◽  
Quantal Release

scholarly journals Seasonal factors influence quantal transmitter release and calcium dependence at amphibian neuromuscular junctions

2017 ◽  
Vol 313 (3) ◽  
pp. R202-R210 ◽  
Author(s):  
Dengyun Ge ◽  
Nickolas Lavidis
Keyword(s):  
Transmitter Release ◽  
Calcium Concentration ◽  
Neuromuscular Junctions ◽  
Release Site ◽  
Extracellular Calcium ◽  
Fourth Power ◽  
Quantal Content ◽  
Wet Season ◽  
Quantal Release ◽  
Extracellular Calcium Concentration

Amphibian neuromuscular junctions (NMJs) are composed of hundreds of neurotransmitter release sites that exhibit nonuniform transmitter release probabilities and demonstrated seasonal modulation. We examined whether recruitment of release sites is variable when the extracellular calcium concentration ([Ca2+]o) is increased in the wet and dry seasons. The amount of transmitter released from the entire nerve terminal increases by approximately the fourth power as [Ca2+]o is increased. Toad ( Bufo marinus) NMJs were visualized using 3,3′-diethyloxardicarbocyanine iodide [DiOC2(5)] fluorescence, and focal loose patch extracellular recordings were used to record the end-plate currents (EPCs) from small groups of release sites. Quantal content ( m̄e), average probability of quantal release ( pe), and the number of active release sites ( ne) were determined for different [Ca2+]o. Our results indicated that the recruitment of quantal release sites with increasing [Ca2+]o differs spatially (between different groups of release sites) and also temporally (in different seasons). These differences were reflected by the nonuniform alterations in pe and ne. Most release site groups demonstrated an increase in both pe and ne when [Ca2+]o increased. In ~30% of release site groups examined, pe decreased while ne increased only during the active period (wet season). Although the dry season induced parallel right shift in the quantal release versus extracellular calcium concentration when compared with the wet season, the dependence of quantal content on [Ca2+]o was not changed. These results demonstrate the flexibility, reserve, and adaptive capacity of neuromuscular junctions in maintaining appropriate levels of neurotransmission.

scholarly journals Measurement of quantal secretion induced by ouabain and its correlation with depletion of synaptic vesicles.

1985 ◽  
Vol 101 (5) ◽  
pp. 1953-1965 ◽  
Author(s):  
C Haimann ◽  
F Torri-Tarelli ◽  
R Fesce ◽  
B Ceccarelli
Keyword(s):  
Synaptic Vesicles ◽  
Time Course ◽  
Neuromuscular Junctions ◽  
Power Spectra ◽  
Peak Frequency ◽  
Fluctuation Analysis ◽  
Experimental Conditions ◽  
Quantal Release ◽  
Release Of Acetylcholine ◽  
Nerve Muscle

Ouabain (0.1 and 0.05 mM) was applied to frog cutaneous pectoris nerve-muscle preparations bathed in modified Ringer's solution containing either 1.8 mM Ca2+ (and 4 mM Mg2+) or no added Ca2+ (4 mM Mg2+ and 1 mM EGTA). During the intense quantal release of acetylcholine (ACh) induced by ouabain, the parameters of the miniature endplate potentials (mepps) were deduced from the variance, skew, and power spectra of the endplate recordings by applying a recently described modification of classical fluctuation analysis. Often the high frequency of mepps is not stationary; therefore, the signal was high-pass filtered (time constant of the resistance-capacitance filter of 2 ms) to remove the errors introduced by nonstationarity. When ouabain was applied in the presence of Ca2+, mepp frequency started to rise exponentially after a lag of 1.5-2 h, reached an average peak frequency of 1,300/s in approximately 30 min, and then suddenly subsided to low level (10/s). In Ca2+-free solution, after a shorter lag (1-1.5 h), mepp frequency rose to peak rate of 700/s in approximately 20 min and then gradually subsided. In spite of the different time course of secretion in the two experimental conditions, the cumulative quantal release was not significantly different (7.4 +/- 1.3 X 10(5) in Ca2+-containing and 8.8 +/- 2.7 X 10(5) in Ca2+-free solutions). 60 min after the peak secretion, the muscles were fixed for observation in the electron microscope. Morphometric analysis on micrographs of neuromuscular junctions revealed in both cases a profound depletion of synaptic vesicles and deep infoldings of presynaptic membrane. This rapid depletion and the lack of uptake of horseradish peroxidase suggest that ouabain impairs the recycling process that tends to conserve the vesicle population during intense secretion of neurotransmitter. The good correlation observed between the reduction in the store of synaptic vesicles and the total number of quanta of ACh secreted in the absence of a vigorous membrane recycling strongly supports the view that the secretion of a quantum of ACh requires the fusion of a synaptic vesicle with the axolemma.

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