Role of NSF in Neurotransmitter Release: A Peptide Microinjection Study at the Crayfish Neuromuscular Junction

2006 ◽  
Vol 96 (3) ◽  
pp. 1053-1060 ◽  
Author(s):  
I. Parnas ◽  
G. Rashkovan ◽  
V. O'Connor ◽  
O. El-Far ◽  
H. Betz ◽  
...  
Keyword(s):  
Amino Acid ◽  
Neuromuscular Junction ◽  
Neurotransmitter Release ◽  
Action Potentials ◽  
Time Course ◽  
Synaptic Delay ◽  
Quantal Content ◽  
Presynaptic Mechanisms ◽  
Crayfish Neuromuscular Junction

Peptides that inhibit the SNAP-stimulated ATPase activity of N-ethylmaleimide-sensitive fusion protein (NSF-2, NSF-3) were injected intra-axonally to study the role of this protein in the release of glutamate at the crayfish neuromuscular junction. Macropatch recording was used to establish the quantal content and to construct synaptic delay histograms. NSF-2 or NSF-3 injection reduced the quantal content, evoked by either direct depolarization of a single release bouton or by axonal action potentials, on average by 66 ± 12% (mean ± SD; n = 32), but had no effect on the time course of release. NSF-2 had no effect on the amplitude or shape of the presynaptic action potential nor on the excitatory nerve terminal current. Neither NSF-2 nor NSF-3 affected the shape or amplitude of single quantal currents. Injection of a peptide with the same composition as NSF-2, but with a scrambled amino acid sequence, failed to alter the quantal content. We conclude that, at the crayfish neuromuscular junction, NSF-dependent reactions regulate quantal content without contributing to the presynaptic mechanisms that control the time course of release.

Different VAMP/Synaptobrevin Complexes for Spontaneous and Evoked Transmitter Release at the Crayfish Neuromuscular Junction

1998 ◽  
Vol 80 (6) ◽  
pp. 3233-3246 ◽  
Author(s):  
Shao-Ying Hua ◽  
Dorota A. Raciborska ◽  
William S. Trimble ◽  
Milton P. Charlton
Keyword(s):  
Neuromuscular Junction ◽  
Transmitter Release ◽  
Neurotransmitter Release ◽  
Action Potentials ◽  
Neuromuscular Junctions ◽  
Spontaneous Release ◽  
Intracellular Ca ◽  
Crayfish Neuromuscular Junction ◽  
Evoked Transmitter Release

Hua, Shao-Ying, Dorota A. Raciborska, William S. Trimble, and Milton P. Charlton. Different VAMP/synaptobrevin complexes for spontaneous and evoked transmitter release at the crayfish neuromuscular junction. J. Neurophysiol. 80: 3233–3246, 1998. Although vesicle-associated membrane protein (VAMP/synaptobrevin) is essential for evoked neurotransmitter release, its role in spontaneous transmitter release remains uncertain. For instance, many studies show that tetanus toxin (TeNT), which cleaves VAMP, blocks evoked transmitter release but leaves some spontaneous transmitter release. We used recombinant tetanus and botulinum neurotoxin catalytic light chains (TeNT-LC, BoNT/B-LC, and BoNT/D-LC) to examine the role of VAMP in spontaneous transmitter release at neuromuscular junctions (nmj) of crayfish. Injection of TeNT-LC into presynaptic axons removed most of the VAMP immunoreactivity and blocked evoked transmitter release without affecting nerve action potentials or Ca2+ influx. The frequency of spontaneous transmitter release was little affected by the TeNT-LC when the evoked transmitter release had been blocked by >95%. The spontaneous transmitter release left after TeNT-LC treatment was insensitive to increases in intracellular Ca2+. BoNT/B-LC, which cleaves VAMP at the same site as TeNT-LC but uses a different binding site, also blocked evoked release but had minimal effect on spontaneous release. However, BoNT/D-LC, which cleaves VAMP at a different site from the other two toxins but binds to the same position on VAMP as TeNT, blocked both evoked and spontaneous transmitter release at similar rates. The data indicate that different VAMP complexes are employed for evoked and spontaneous transmitter release; the VAMP used in spontaneous release is not readily cleaved by TeNT or BoNT/B. Because the exocytosis that occurs after the action of TeNT cannot be increased by increased intracellular Ca2+, the final steps in neurotransmitter release are Ca2+ independent.

scholarly journals Role of α-SNAP in Promoting Efficient Neurotransmission at the Crayfish Neuromuscular Junction

1999 ◽  
Vol 82 (6) ◽  
pp. 3406-3416 ◽  
Author(s):  
Ping He ◽  
R. Chase Southard ◽  
Dong Chen ◽  
S. W. Whiteheart ◽  
R. L. Cooper
Keyword(s):  
Neuromuscular Junction ◽  
Neurotransmitter Release ◽  
Synaptic Vesicles ◽  
Synaptic Current ◽  
Attachment Protein ◽  
Quantal Analysis ◽  
Sensitive Factor ◽  
Electrophysiological Studies ◽  
Crayfish Neuromuscular Junction

In this manuscript, we address the role of the soluble N-ethylmaleimide sensitive factor attachment protein (α-SNAP) in synaptic transmission at the neuromuscular junction of the crayfish opener muscle. Immunochemcial methods confirm the presence of α-SNAP in these preparations and show that it is concentrated in the synaptic areas. Microinjection and electrophysiological studies show that α-SNAP causes an increase in neurotransmitter release yet does not significantly affect the kinetics. More specific quantal analysis, using focal, macropatch, synaptic current recordings, shows that α-SNAP increases transmitter release by increasing the probability of exocytosis but not the number of potential release sites. These data demonstrate that the role of α-SNAP is to increase the efficiency of neurotransmission by increasing the probability that a stimulus will result in neurotransmitter release. What this suggests is that α-SNAP is critical for the formation and maintenance of a “ready release” pool of synaptic vesicles.

Differences in presynaptic action of 4-aminopyridine and tetraethylammonium at frog neuromuscular junction

1987 ◽  
Vol 65 (5) ◽  
pp. 747-752 ◽  
Author(s):  
M. I. Glavinović
Keyword(s):  
Neuromuscular Junction ◽  
Transmitter Release ◽  
Action Potentials ◽  
Time Course ◽  
Potassium Conductance ◽  
Frog Neuromuscular Junction ◽  
Quantal Content ◽  
Low Concentrations ◽  
Voltage Dependent ◽  
Intracellular Ca

4-Aminopyridine markedly potentiates transmitter release at the frog cutaneous pectoris neuromuscular junction by increasing the quantal content even when applied at low concentrations (5–20 μM). This enhancement of transmitter release is associated with greater minimum synaptic latency, but the dispersion of the synaptic latencies does not appear much affected. This is in contrast with the action of tetraethylammonium (0.2–0.5 mM) in which case similar enhancement of transmitter release results not only in larger minimum synaptic latency but also in greater dispersion of the synaptic latencies. The time course of transmitter release associated with enhanced transmitter output is hence much more prolonged in the presence of tetraethylammonium than 4-aminopyridine, at least for low concentrations of 4-aminopyridine (5–20 μM). This indicates that their presynaptic actions differ significantly. This conclusion is further strengthened by the finding that unlike tetraethylammonium, 4-aminopyridine induces bursts of release, presumably by producing multiple action potentials in the nerve terminal. Tetraethylammonium probably acts by blocking the delayed potassium conductance, but the blockade of Ca2+-activated K+ conductance cannot be excluded. 4-Aminopyridine, however, probably blocks the fast inactivating (IA) K+ current, but it also may be acting directly on the voltage-dependent Ca2+ conductance or on the intracellular Ca2+ buffering.

scholarly journals Role of Rab3 GDP/GTP Exchange Protein in Synaptic Vesicle Trafficking at the Mouse Neuromuscular Junction

2001 ◽  
Vol 12 (5) ◽  
pp. 1421-1430 ◽  
Author(s):  
Miki Tanaka ◽  
Jun Miyoshi ◽  
Hiroyoshi Ishizaki ◽  
Atsushi Togawa ◽  
Katsunori Ohnishi ◽  
...  
Keyword(s):  
Neuromuscular Junction ◽  
Neurotransmitter Release ◽  
Synaptic Vesicles ◽  
Action Potentials ◽  
Axonal Conduction ◽  
Small G Protein ◽  
Presynaptic Plasma Membrane ◽  
Gastrocnemius Muscles ◽  
Exchange Protein

The Rab3 small G protein family consists of four members, Rab3A, -3B, -3C, and -3D. Of these members, Rab3A regulates Ca2+-dependent neurotransmitter release. These small G proteins are activated by Rab3 GDP/GTP exchange protein (Rab3 GEP). To determine the function of Rab3 GEP during neurotransmitter release, we have knocked out Rab3 GEP in mice. Rab3 GEP−/− mice developed normally but died immediately after birth. Embryos at E18.5 showed no evoked action potentials of the diaphragm and gastrocnemius muscles in response to electrical stimulation of the phrenic and sciatic nerves, respectively. In contrast, axonal conduction of the spinal cord and the phrenic nerve was not impaired. Total numbers of synaptic vesicles, especially those docked at the presynaptic plasma membrane, were reduced at the neuromuscular junction ∼10-fold compared with controls, whereas postsynaptic structures and functions appeared normal. Thus, Rab3 GEP is essential for neurotransmitter release and probably for formation and trafficking of the synaptic vesicles.

scholarly journals SLO-1 Potassium Channels Control Quantal Content of Neurotransmitter Release at the C. elegans Neuromuscular Junction

Neuron ◽  
2001 ◽  
Vol 32 (5) ◽  
pp. 867-881 ◽  
Author(s):  
Zhao-Wen Wang ◽  
Owais Saifee ◽  
Michael L. Nonet ◽  
Lawrence Salkoff
Keyword(s):  
Potassium Channels ◽  
Neuromuscular Junction ◽  
Neurotransmitter Release ◽  
Quantal Content ◽  
C Elegans

scholarly journals Role of intracellular Ca2+ in stimulation-induced increases in transmitter release at the frog neuromuscular junction.

1994 ◽  
Vol 104 (2) ◽  
pp. 337-355 ◽  
Author(s):  
J E Zengel ◽  
M A Sosa ◽  
R E Poage ◽  
D R Mosier
Keyword(s):  
Neuromuscular Junction ◽  
Transmitter Release ◽  
Cyclopiazonic Acid ◽  
Progressive Increase ◽  
Repetitive Stimulation ◽  
Frog Neuromuscular Junction ◽  
Quantal Content ◽  
Carbonyl Cyanide ◽  
Stimulation Of

Under conditions of reduced quantal content, repetitive stimulation of a presynaptic nerve can result in a progressive increase in the amount of transmitter released by that nerve in response to stimulation. At the frog neuromuscular junction, this increase in release has been attributed to four different processes: first and second components of facilitation, augmentation, and potentiation (e.g., Zengel, J. E., and K. L. Magleby. 1982. Journal of General Physiology. 80:583-611). It has been suggested that an increased entry of Ca2+ or an accumulation of intraterminal Ca2+ may be responsible for one or more of these processes. To test this hypothesis, we have examined the role of intracellular Ca2+ in mediating changes in end-plate potential (EPP) amplitude during and after repetitive stimulation at the frog neuromuscular junction. We found that increasing the extracellular Ca2+ concentration or exposing the preparation to carbonyl cyanide m-chlorophenylhydrazone, ionomycin, or cyclopiazonic acid all led to a greater increase in EPP amplitude during conditioning trains of 10-200 impulses applied at a frequency of 20 impulses/s. These experimental manipulations, all of which have been shown to increase intracellular levels of Ca2+, appeared to act by increasing primarily the augmentation component of increased release. The results of this study are consistent with previous suggestions that the different components of increased release represent different mechanisms, and that Ca2+ may be acting at more than one site in the nerve terminal.

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