Effect of hypertonic saline on quantal size and synaptic vesicles in identified neuromuscular junction of the frog

Neuroscience ◽  
1987 ◽  
Vol 23 (2) ◽  
pp. 745-756 ◽  
Author(s):  
M.E. Kriebel ◽  
G.D. Pappas
Keyword(s):  
Neuromuscular Junction ◽  
Hypertonic Saline ◽  
Synaptic Vesicles ◽  
Quantal Size

scholarly journals A novel and specific regulator of neuronal V-ATPase in Drosophila

2021 ◽  
Author(s):  
Amina Dulac ◽  
Abdul-Raouf Issa ◽  
Jun Sun ◽  
Giorgio Matassi ◽  
Baya Chérif-Zahar ◽  
...  
Keyword(s):  
Neuromuscular Junction ◽  
Proton Pump ◽  
Sequence Homology ◽  
Neurotransmitter Release ◽  
Synaptic Vesicles ◽  
Eukaryotic Cells ◽  
Its Sequence ◽  
Quantal Size ◽  
Atpase Subunits ◽  
Enzymatic Complex

AbstractThe V-ATPase is a highly conserved enzymatic complex that ensures appropriate levels of organelle acidification in virtually all eukaryotic cells. While the general mechanisms of this proton pump have been well studied, little is known about the specific regulations of neuronal V-ATPase. Here, we studied CG31030, a previously uncharacterized Drosophila protein predicted from its sequence homology to be part of the V-ATPase family. We found that this protein is essential and apparently specifically expressed in neurons, where it is addressed to synaptic terminals. We observed that CG31030 co-immunoprecipitated with V-ATPase subunits, in particular with ATP6AP2, and that synaptic vesicles of larval motoneurons were not properly acidified in CG31030 knockdown context. This defect was associated with a decrease in quantal size at the neuromuscular junction, severe locomotor impairments and shortened lifespan. Overall, our data provide evidence that CG31030 is a specific regulator of neuronal V-ATPase that is required for synaptic vesicle acidification and neurotransmitter release.

scholarly journals An essential role of acetylcholine-glutamate synergy at habenular synapses in nicotine dependence

eLife ◽  
2015 ◽  
Vol 4 ◽  
Author(s):  
Silke Frahm ◽  
Beatriz Antolin-Fontes ◽  
Andreas Görlich ◽  
Johannes-Friedrich Zander ◽  
Gudrun Ahnert-Hilger ◽  
...  
Keyword(s):  
Synaptic Vesicles ◽  
Critical Role ◽  
Conditioned Reward ◽  
Quantal Size ◽  
Medial Habenula ◽  
Vesicular Transporters ◽  
Circuit Function ◽  
And Behavior ◽  
Presynaptic Facilitation

A great deal of interest has been focused recently on the habenula and its critical role in aversion, negative-reward and drug dependence. Using a conditional mouse model of the ACh-synthesizing enzyme choline acetyltransferase (Chat), we report that local elimination of acetylcholine (ACh) in medial habenula (MHb) neurons alters glutamate corelease and presynaptic facilitation. Electron microscopy and immuno-isolation analyses revealed colocalization of ACh and glutamate vesicular transporters in synaptic vesicles (SVs) in the central IPN. Glutamate reuptake in SVs prepared from the IPN was increased by ACh, indicating vesicular synergy. Mice lacking CHAT in habenular neurons were insensitive to nicotine-conditioned reward and withdrawal. These data demonstrate that ACh controls the quantal size and release frequency of glutamate at habenular synapses, and suggest that the synergistic functions of ACh and glutamate may be generally important for modulation of cholinergic circuit function and behavior.

scholarly journals Depolarization-Induced Ca2+ Entry Preferentially Evokes Release of Large Quanta in the Developing Xenopus Neuromuscular Junction

2010 ◽  
Vol 104 (5) ◽  
pp. 2730-2740 ◽  
Author(s):  
Xiao-Ping Sun ◽  
Bo-Ming Chen ◽  
Olav Sand ◽  
Yoshi Kidokoro ◽  
Alan D. Grinnell
Keyword(s):  
Synaptic Vesicles ◽  
Channel Blocker ◽  
Direct Injection ◽  
External Solution ◽  
Neuromuscular Synapses ◽  
Quantal Size ◽  
Amplitude Histogram ◽  
Wide Range ◽  
Patch Pipette ◽  
Second Peak

The amplitude histogram of spontaneously occurring miniature synaptic currents (mSCs) is skewed positively at developing Xenopus neuromuscular synapses formed in culture. To test whether the quantal size of nerve-evoked quanta (eSCs) distributes similarly, we compared the amplitude histogram of single quantum eSCs in low external Ca2+ with that of mSCs and found that nerve stimulation preferentially released large quanta. Depolarization of presynaptic terminals by elevating [K+] in the external solution or by direct injection of current through a patch pipette increased the mSC frequency and preferentially, but not exclusively, evoked the release of large quanta, resulting in a second broad peak in the amplitude histogram. Formation of the second peak under these conditions was blocked by the N-type Ca2+ channel blocker, ω-conotoxin GVIA. In contrast, when the mSC frequency was elevated by thapsigargin- or caffeine-induced mobilization of internal Ca2+, formation of the second peak did not occur. We conclude that the second peak in the amplitude histogram is generated by Ca2+ influx through N-type Ca2+ channels, causing a local elevation of internal Ca2+. The mSC amplitude in the positively skewed portion of the histogram varied over a wide range. A competitive blocker of acetylcholine (ACh) receptors, d-tubocurarine, reduced the amplitude of smaller mSCs in this range relatively more than that of larger mSCs, suggesting that this variation in the mSC amplitude is due to variable amounts of ACh released from synaptic vesicles. We suggest that Ca2+ influx through N-type Ca2+ channels preferentially induces release of vesicles with large ACh content.

scholarly journals THE LOCALIZATION OF ACETYLCHOLINESTERASE AT THE AUTONOMIC NEUROMUSCULAR JUNCTION

1967 ◽  
Vol 33 (1) ◽  
pp. 93-102 ◽  
Author(s):  
Peter M. Robinson ◽  
Christopher Bell
Keyword(s):  
Enzyme Activity ◽  
Smooth Muscle ◽  
Neuromuscular Junction ◽  
Smooth Muscle Cells ◽  
Schwann Cells ◽  
Synaptic Vesicles ◽  
Muscle Cells ◽  
Acetylcholinesterase Activity ◽  
Bufo Marinus ◽  
Toad Bufo

Acetylcholinesterase has been localized at the autonomic neuromuscular junction in the bladder of the toad (Bufo marinus) by the Karnovsky method. High levels of enzyme activity have been demonstrated in association with the membranes of cholinergic axons and the adjacent membranes of the accompanying Schwann cells. The synaptic vesicles stained in occasional cholinergic axons. After longer incubation times, the membrane of smooth muscle cells close to cholinergic axons also stained. Axons with only moderate acetylcholinesterase activity or with no activity at all were seen in the same bundles as cholinergic axons, but identification of the transmitter in these axons was not possible.

Quantal Unit Populations at the DrosophilaLarval Neuromuscular Junction

1999 ◽  
Vol 82 (3) ◽  
pp. 1497-1511 ◽  
Author(s):  
K. Wong ◽  
S. Karunanithi ◽  
H. L. Atwood
Keyword(s):  
Neuromuscular Junction ◽  
Time Course ◽  
Extracellular Recording ◽  
Intracellular Recordings ◽  
Quantal Size ◽  
Extracellular Signal ◽  
Spontaneous Frequency ◽  
The Individual ◽  
High Level ◽  
Larval Neuromuscular Junction

Focal extracellular recording at visualized boutons of the Drosophila larval neuromuscular junction was used to determine frequency and time course of the spontaneously occurring quantal events. When simultaneous intracellular recordings from the innervated muscle cell were made, more than one class of quantal event occurred at some of the individual boutons. “True” signals (arising at the bouton within the focal macropatch electrode) were often contaminated by additional signals generated outside the lumen of the focal electrode. Inclusion of these contaminating signals gave spuriously low values for relative amplitude, and spuriously high values for spontaneous quantal emission, for the synapses within the focal electrode. The contaminating signals, which appeared to be conducted along the subsynaptic reticulum surrounding the nerve terminals, generally were characterized by relatively small extracellular signals associated with normal intracellular events in the muscle fiber. From plots of simultaneous extracellular and intracellular recordings, the individual data points were classified according to the angles they subtended with the x axis (extracellular signal axis). Statistical procedures were developed to separate the true signals and contaminants with a high level of confidence. Populations of quantal events were found to be well described by Gaussian mixtures of two or three components, one of which could be characterized as the true signal population. Separation of signals from contaminants provides a basis for improving the estimates of quantal size and spontaneous frequency for the synapses sampled by the focal extracellular electrode.

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