Identification of excitatory and inhibitory neuromuscular synapses in the crayfish thoracic deep flexor musculature

1981 ◽  
Vol 59 (3) ◽  
pp. 364-369
Author(s):  
R. L. Crabtree ◽  
R. G. Sherman
Keyword(s):  
Electron Microscopy ◽  
Synaptic Vesicle ◽  
Synaptic Vesicles ◽  
Synaptic Cleft ◽  
Nerve Terminals ◽  
Neuromuscular Synapses ◽  
Deep Flexors

Excitatory and inhibitory neuromuscular synapses in the thoracic deep flexors of the crayfish were examined using electron microscopy. Excitatory nerve terminals were found to have larger synaptic vesicles and a greater synaptic cleft distance than did inhibitory terminals. These results were confirmed by fixation enhancement of differences in synaptic vesicle morphology and the experimental depletion of vesicles in the excitatory nerve terminals.

scholarly journals An antiserum specific for cholinergic synaptic vesicles from electric organ.

1980 ◽  
Vol 87 (1) ◽  
pp. 98-103 ◽  
Author(s):  
S S Carlson ◽  
R B Kelly
Keyword(s):  
Synaptic Vesicle ◽  
Synaptic Vesicles ◽  
Membrane Fraction ◽  
Motor Nerve ◽  
Buoyant Density ◽  
Electric Organ ◽  
Rabbit Serum ◽  
Antigenic Determinants ◽  
Nerve Terminals ◽  
Isopycnic Centrifugation

Rabbit antisera to highly purified synaptic vesicles from the electric organ of Narcine brasiliensis, an electric ray, reveal a unique population of synaptic vesicle antigens in addition to a population shared with other electric organ membranes. Synaptic vesicle antigens were detected by binding successively rabbit antivesicle serum and radioactive goat anti-rabbit serum. To remove antibodies directed against antigens common to synaptic vesicles and other electric organ fractions, the antivesicle serum was extensively preadsorbed against an electric organ membrane fraction that was essentially free of synaptic vesicles. The adsorbed serum retained 40% of its ability to bind to synaptic vesicles, suggesting that about half of the antigenic determinants are unique. Vesicle antigens were quantified with a radioimmunoassay (RIA) that utilized precipitation of antibody-antigen complexes with Staphylococcus aureus cells. By this assay, the vesicles, detected by their acetylcholine (ACh) content and the antigens detected by the RIA, have the same buoyant density after isopycnic centrifugation of crude membrane fractions on sucrose and glycerol density gradients. The ratio of ACh to antigenicity was constant across the vesicle peaks and was close to that observed for vesicles purified to homogeneity. Even though the vesicles make up only approximately 0.5% of the material in the original homogenate, the ratio of acetylcholine to vesicle antigenicity could still be measured and also was indistinguishable from that of pure vesicles. We conclude that synaptic vesicles contain unique antigenic determinants not present to any measurable extent in other fractions of the electric organ. Consequently, it is possible to raise a synaptic vesicle-specific antiserum that allows vesicles to be detected and quantified. These findings are consistent with earlier immunohistochemical observations of specific antibody binding to motor nerve terminals.

Neurotransmitter Release

2017 ◽  
Author(s):  
Peggy Mason
Keyword(s):  
Plasma Membrane ◽  
Synaptic Vesicle ◽  
Active Zone ◽  
Neurotransmitter Release ◽  
Synaptic Vesicles ◽  
Synaptic Cleft ◽  
Fusion Pore ◽  
Synaptic Membrane ◽  
Specialized Region ◽  
Synaptic Vesicle Fusion

The biochemical and physiological processes of neurotransmitter release from an active zone, a specialized region of synaptic membrane, are examined. Synaptic vesicles containing neurotransmitters are docked at the active zone and then primed for release by SNARE complexes that bring them into extreme proximity to the plasma membrane. Entry of calcium ions through voltage-gated calcium channels triggers synaptic vesicle fusion with the synaptic terminal membrane and the consequent diffusion of neurotransmitter into the synaptic cleft. Release results when the fusion pore bridging the synaptic vesicle and plasma membrane widens and neurotransmitter from the inside of the synaptic vesicle diffuses into the synaptic cleft. Membrane from the active zone membrane is endocytosed, and synaptic vesicle proteins are then reassembled into recycled synaptic vesicles, allowing for more rounds of neurotransmitter release.

Impairment of Synaptic Vesicle Exocytosis and Recycling During Neuromuscular Weakness Produced in Mice by 2,4-Dithiobiuret

2002 ◽  
Vol 88 (6) ◽  
pp. 3243-3258 ◽  
Author(s):  
You-Fen Xu ◽  
Dawn Autio ◽  
Mary B. Rheuben ◽  
William D. Atchison
Keyword(s):  
Synaptic Vesicle ◽  
Muscle Weakness ◽  
Nerve Stimulation ◽  
Synaptic Vesicles ◽  
Motor Nerve ◽  
Neuromuscular Disorders ◽  
Neuroaxonal Dystrophy ◽  
Nerve Terminals ◽  
Synaptic Vesicle Exocytosis ◽  
Vesicle Exocytosis

Chronic treatment of rodents with 2,4-dithiobiuret (DTB) induces a neuromuscular syndrome of flaccid muscle weakness that mimics signs seen in several human neuromuscular disorders such as congenital myasthenic syndromes, botulism, and neuroaxonal dystrophy. DTB-induced muscle weakness results from a reduction of acetylcholine (ACh) release by mechanisms that are not yet clear. The objective of this study was to determine if altered release of ACh during DTB-induced muscle weakness was due to impairments of synaptic vesicle exocytosis, endocytosis, or internal vesicular processing. We examined motor nerve terminals in the triangularis sterni muscles of DTB-treated mice at the onset of muscle weakness. Uptake of FM1-43, a fluorescent marker for endocytosis, was reduced to approximately 60% of normal after either high-frequency nerve stimulation or K+depolarization. Terminals ranged from those with nearly normal fluorescence (“bright terminals”) to terminals that were poorly labeled (“dim terminals”). Ultrastructurally, the number of synaptic vesicles that were labeled with horseradish peroxidase (HRP) was also reduced by DTB to approximately 60%; labeling among terminals was similarly variable. A subset of DTB-treated terminals having abnormal tubulovesicular profiles in their centers did not respond to stimulation with increased uptake of HRP and may correspond to dim terminals. Two findings suggest that posttetanic “slow endocytosis” remained qualitatively normal: the rate of this type of endocytosis as measured with FM1-43 did not differ from normal, and HRP was observed in organelles associated with this pathway- coated vesicles, cisternae, as well as synaptic vesicles but not in the tubulovesicular profiles. In DTB-treated bright terminals, end-plate potential (EPP) amplitudes were decreased, and synaptic depression in response to 15-Hz stimulation was increased compared with those of untreated mice; in dim terminals, EPPs were not observed during block withd-tubocurarine. Nerve-stimulation-induced unloading of FM1-43 was slower and less complete than normal in bright terminals, did not occur in dim terminals, and was not enhanced by α-latrotoxin. Collectively, these results indicate that the size of the recycling vesicle pool is reduced in nerve terminals during DTB-induced muscle weakness. The mechanisms by which this reduction occurs are not certain, but accumulated evidence suggests that they may include defects in either or both exocytosis and internal vesicular processing.

Putative duality of presynaptic events

2016 ◽  
Vol 27 (4) ◽  
pp. 377-383 ◽  
Author(s):  
Tatiana Borisova ◽  
Arsenii Borysov
Keyword(s):  
Synaptic Vesicles ◽  
Signal Transmission ◽  
Synaptic Cleft ◽  
Long Term Potentiation ◽  
Nerve Terminals ◽  
Chemical Synapse ◽  
Excitatory Neurotransmitter ◽  
Glutamate Concentration ◽  
Nerve Signal ◽  
Compound Exocytosis

AbstractThe main structure in the brain responsible not only for nerve signal transmission but also for its simultaneous regulation is chemical synapse, where presynaptic nerve terminals are of considerable importance providing release of neurotransmitters. Analyzing transport of glutamate, the major excitatory neurotransmitter in the mammalian CNS, the authors suggest that there are two main relatively independent mechanisms at the presynaptic level that can influence the extracellular glutamate concentration, and so signaling, and its regulation. The first one is well-known precisely regulated compound exocytosis of synaptic vesicles containing neurotransmitters stimulated by membrane depolarization, which increases significantly glutamate concentration in the synaptic cleft and initiates glutamate signaling through postsynaptic glutamate receptors. The second one is permanent glutamate turnover across the plasma membrane that occurs without stimulation and is determined by simultaneous non-pathological transporter-mediated release of glutamate thermodynamically synchronized with uptake. Permanent glutamate turnover is responsible for maintenance of dynamic glutamatein/glutamateoutgradient resulting in the establishment of a flexible extracellular level of glutamate, which can be unique for each synapse because of dependence on individual presynaptic parameters. These two mechanisms, i.e. exocytosis and transporter-mediated glutamate turnover, are both precisely regulated but do not directly interfere with each other, because they have different intracellular sources of glutamate in nerve terminals for release purposes, i.e. glutamate pool of synaptic vesicles and the cytoplasm, respectively. This duality can set up a presynaptic base for memory consolidation and storage, maintenance of neural circuits, long-term potentiation, and plasticity. Arguments against this suggestion are also considered.

scholarly journals The synaptic vesicle cycle: a single vesicle budding step involving clathrin and dynamin.

1996 ◽  
Vol 133 (6) ◽  
pp. 1237-1250 ◽  
Author(s):  
K Takei ◽  
O Mundigl ◽  
L Daniell ◽  
P De Camilli
Keyword(s):  
Plasma Membrane ◽  
Synaptic Vesicle ◽  
Synaptic Vesicles ◽  
Hippocampal Neurons ◽  
Coated Vesicles ◽  
Coated Vesicle ◽  
Nerve Terminals ◽  
Vesicle Budding ◽  
Vesicle Cycle ◽  
Single Vesicle

Strong evidence implicates clathrin-coated vesicles and endosome-like vacuoles in the reformation of synaptic vesicles after exocytosis, and it is generally assumed that these vacuoles represent a traffic station downstream from clathrin-coated vesicles. To gain insight into the mechanisms of synaptic vesicle budding from endosome-like intermediates, lysed nerve terminals and nerve terminal membrane subfractions were examined by EM after incubations with GTP gamma S. Numerous clathrin-coated budding intermediates that were positive for AP2 and AP180 immunoreactivity and often collared by a dynamin ring were seen. These were present not only on the plasma membrane (Takei, K., P.S. McPherson, S.L.Schmid, and P. De Camilli. 1995. Nature (Lond.). 374:186-190), but also on internal vacuoles. The lumen of these vacuoles retained extracellular tracers and was therefore functionally segregated from the extracellular medium, although narrow connections between their membranes and the plasmalemma were sometimes visible by serial sectioning. Similar observations were made in intact cultured hippocampal neurons exposed to high K+ stimulation. Coated vesicle buds were generally in the same size range of synaptic vesicles and positive for the synaptic vesicle protein synaptotagmin. Based on these results, we suggest that endosome-like intermediates of nerve terminals originate by bulk uptake of the plasma membrane and that clathrin- and dynamin-mediated budding takes place in parallel from the plasmalemma and from these internal membranes. We propose a synaptic vesicle recycling model that involves a single vesicle budding step mediated by clathrin and dynamin.

scholarly journals Retrieval and recycling of synaptic vesicle membrane in pinched-off nerve terminals (synaptosomes).

1978 ◽  
Vol 78 (3) ◽  
pp. 685-700 ◽  
Author(s):  
R C Fried ◽  
M P Blaustein
Keyword(s):  
Synaptic Vesicle ◽  
Synaptic Vesicles ◽  
Plasma Membranes ◽  
Large Diameter ◽  
Small Diameter ◽  
Physiological Saline ◽  
Nerve Terminals ◽  
Vesicle Membrane ◽  
Thorium Dioxide ◽  
Vesicular Exocytosis

The morphological features of pinched-off presynaptic nerve terminals (synaptosomes) from rat brain were examined with electron microscope techniques; in many experiments, an extracellular marked (horseradish peroxidase or colloidal thorium dioxide) was included in the incubation media. When incubated in physiological saline, most terminals appeared approximately spherical, and were filled with small (approximately 400-A diameter) "synaptic vesicles"; mitochondria were also present in many of the terminals. In a number of instances the region of synaptic contact, with adhering portions of the postsynaptic cell membrane and postsynaptic density, could be readily discerned. Approximately 20--30% of the terminals in our preparations exhibited clear evidence of damage, as indicated by diffuse distribution of extracellular markers in the cytoplasm; the markers appeared to be excluded from the intraterminal vesicles under these circumstances. The markers were excluded from the cytoplasm in approximately 70--80% of the terminals, which may imply that these terminals have intact plasma membranes. When the terminals were treated with depolarizing agents (veratridine or K-rich media), in the presence of Ca, many new, large (600--900-A diameter) vesicles and some coated vesicles and new vacuoles appeared. When the media contained an extracellular marker, the newly formed structures frequently were labeled with the marker. If the veratridine-depolarized terminals were subsequently treated with tetrodotoxin (to repolarize the terminals) and allowed to "recover" for 60--90 min, most of the large marker-containing vesicles disappeared, and numerous small (approximately 400-A diameter) marker-containing vesicles appeared. These observations are consistent with the idea that pinched-off presynaptic terminals contain all of the machinery necessary for vesicular exocytosis and for the retrieval and recycling of synaptic vesicle membrane. The vesicle membrane appears to be retrieval primarily in the form of large diameter vesicles which are subsequently reprocessed to form new "typical" small-diameter synaptic vesicles.

scholarly journals EVIDENCE FOR RECYCLING OF SYNAPTIC VESICLE MEMBRANE DURING TRANSMITTER RELEASE AT THE FROG NEUROMUSCULAR JUNCTION

1973 ◽  
Vol 57 (2) ◽  
pp. 315-344 ◽  
Author(s):  
J. E. Heuser ◽  
T. S. Reese
Keyword(s):  
Plasma Membrane ◽  
Synaptic Vesicle ◽  
Synaptic Vesicles ◽  
Motor Nerve ◽  
Coated Vesicles ◽  
Synaptic Membrane ◽  
Nerve Terminals ◽  
Frog Neuromuscular Junction ◽  
Vesicle Membrane ◽  
Intracellular Compartments

When the nerves of isolated frog sartorius muscles were stimulated at 10 Hz, synaptic vesicles in the motor nerve terminals became transiently depleted. This depletion apparently resulted from a redistribution rather than disappearance of synaptic vesicle membrane, since the total amount of membrane comprising these nerve terminals remained constant during stimulation. At 1 min of stimulation, the 30% depletion in synaptic vesicle membrane was nearly balanced by an increase in plasma membrane, suggesting that vesicle membrane rapidly moved to the surface as it might if vesicles released their content of transmitter by exocytosis. After 15 min of stimulation, the 60% depletion of synaptic vesicle membrane was largely balanced by the appearance of numerous irregular membrane-walled cisternae inside the terminals, suggesting that vesicle membrane was retrieved from the surface as cisternae. When muscles were rested after 15 min of stimulation, cisternae disappeared and synaptic vesicles reappeared, suggesting that cisternae divided to form new synaptic vesicles so that the original vesicle membrane was now recycled into new synaptic vesicles. When muscles were soaked in horseradish peroxidase (HRP), this tracerfirst entered the cisternae which formed during stimulation and then entered a large proportion of the synaptic vesicles which reappeared during rest, strengthening the idea that synaptic vesicle membrane added to the surface was retrieved as cisternae which subsequently divided to form new vesicles. When muscles containing HRP in synaptic vesicles were washed to remove extracellular HRP and restimulated, HRP disappeared from vesicles without appearing in the new cisternae formed during the second stimulation, confirming that a one-way recycling of synaptic membrane, from the surface through cisternae to new vesicles, was occurring. Coated vesicles apparently represented the actual mechanism for retrieval of synaptic vesicle membrane from the plasma membrane, because during nerve stimulation they proliferated at regions of the nerve terminals covered by Schwann processes, took up peroxidase, and appeared in various stages of coalescence with cisternae. In contrast, synaptic vesicles did not appear to return directly from the surface to form cisternae, and cisternae themselves never appeared directly connected to the surface. Thus, during stimulation the intracellular compartments of this synapse change shape and take up extracellular protein in a manner which indicates that synaptic vesicle membrane added to the surface during exocytosis is retrieved by coated vesicles and recycled into new synaptic vesicles by way of intermediate cisternae.

scholarly journals Redistribution of synaptophysin and synapsin I during alpha-latrotoxin-induced release of neurotransmitter at the neuromuscular junction.

1990 ◽  
Vol 110 (2) ◽  
pp. 449-459 ◽  
Author(s):  
F Torri-Tarelli ◽  
A Villa ◽  
F Valtorta ◽  
P De Camilli ◽  
P Greengard ◽  
...  
Keyword(s):  
Synaptic Vesicle ◽  
Synaptic Vesicles ◽  
Low Dose ◽  
Synapsin I ◽  
Nerve Terminals ◽  
Frozen Sections ◽  
Vesicle Membrane ◽  
Ultrathin Frozen Sections ◽  
Nerve Muscle ◽  
Molecular Components

The distribution of two synaptic vesicle-specific phosphoproteins, synaptophysin and synapsin I, during intense quantal secretion was studied by applying an immunogold labeling technique to ultrathin frozen sections. In nerve-muscle preparations treated for 1 h with a low dose of alpha-latrotoxin in the absence of extracellular Ca2+ (a condition under which nerve terminals are depleted of both quanta of neurotransmitter and synaptic vesicles), the immunolabeling for both proteins was distributed along the axolemma. These findings indicate that, in the presence of a block of endocytosis, exocytosis leads to the permanent incorporation of the synaptic vesicle membrane into the axolemma and suggest that, under this condition, at least some of the synapsin I molecules remain associated with the vesicle membrane after fusion. When the same dose of alpha-latrotoxin was applied in the presence of extracellular Ca2+, the immunoreactivity patterns resembled those obtained in resting preparations: immunogold particles were selectively associated with the membrane of synaptic vesicles, whereas the axolemma was virtually unlabeled. Under this condition an active recycling of both quanta of neurotransmitter and vesicles operates. These findings indicate that the retrieval of components of the synaptic vesicle membrane is an efficient process that does not involve extensive intermixing between molecular components of the vesicle and plasma membrane, and show that synaptic vesicles that are rapidly recycling still have the bulk of synapsin I associated with their membrane.

scholarly journals Colocalization of synapsin and actin during synaptic vesicle recycling

2003 ◽  
Vol 161 (4) ◽  
pp. 737-747 ◽  
Author(s):  
Ona Bloom ◽  
Emma Evergren ◽  
Nikolay Tomilin ◽  
Ole Kjaerulff ◽  
Peter Löw ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Synaptic Vesicle ◽  
Active Zone ◽  
Synaptic Vesicles ◽  
Synaptic Activity ◽  
Immunogold Electron Microscopy ◽  
Synaptic Vesicle Recycling ◽  
Vesicle Recycling ◽  
Reserve Pool ◽  
Giant Synapse

It has been hypothesized that in the mature nerve terminal, interactions between synapsin and actin regulate the clustering of synaptic vesicles and the availability of vesicles for release during synaptic activity. Here, we have used immunogold electron microscopy to examine the subcellular localization of actin and synapsin in the giant synapse in lamprey at different states of synaptic activity. In agreement with earlier observations, in synapses at rest, synapsin immunoreactivity was preferentially localized to a portion of the vesicle cluster distal to the active zone. During synaptic activity, however, synapsin was detected in the pool of vesicles proximal to the active zone. In addition, actin and synapsin were found colocalized in a dynamic filamentous cytomatrix at the sites of synaptic vesicle recycling, endocytic zones. Synapsin immunolabeling was not associated with clathrin-coated intermediates but was found on vesicles that appeared to be recycling back to the cluster. Disruption of synapsin function by microinjection of antisynapsin antibodies resulted in a prominent reduction of the cytomatrix at endocytic zones of active synapses. Our data suggest that in addition to its known function in clustering of vesicles in the reserve pool, synapsin migrates from the synaptic vesicle cluster and participates in the organization of the actin-rich cytomatrix in the endocytic zone during synaptic activity.

scholarly journals Hydrodynamics govern the pre-fusion docking time of synaptic vesicles

2018 ◽  
Vol 15 (138) ◽  
pp. 20170818
Author(s):  
Pankaj Singh ◽  
Chung-Yuen Hui
Keyword(s):  
Synaptic Vesicle ◽  
Synaptic Vesicles ◽  
Driving Force ◽  
Lipid Membrane ◽  
Synaptic Cleft ◽  
Fusion Pore ◽  
Ribbon Synapses ◽  
Experimental Findings ◽  
Synaptic Vesicle Fusion ◽  
Ribbon Structures

Synaptic vesicle fusion is a crucial step in the neurotransmission process. Neurotransmitter-filled vesicles are pre-docked at the synapse by the mediation of ribbon structures and SNARE proteins at the ribbon synapses. An electrical impulse triggers the fusion process of pre-docked vesicles, leading to the formation of a fusion pore and subsequently resulting in the release of neurotransmitter into the synaptic cleft. In this study, a continuum model of lipid membrane along with lubrication theory is used to determine the traverse time of the synaptic vesicle under the influence of hydrodynamic forces. We find that the traverse time is strongly dependent on how fast the driving force decays or grows with closure of the gap between the vesicle and the plasma membrane. If the correct behaviour is chosen, the traverse time obtained is of the order of a few hundred milliseconds and lies within the experimentally obtained value of approximately 250 ms (Zenisek D, Steyer JA, Almers W. 2000 Nature 406 , 849–854 ( doi:10.1038/35022500 )). We hypothesize that there are two different force behaviours, which complies with the experimental findings of pre-fusion docking of synaptic vesicles at the ribbon synapses. The common theme in the proposed force models is that the driving force has to very rapidly increase or decrease with the amount of clamping.

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