Release of Transmitter from Degenerating Locust Motorneurones

1973 ◽  
Vol 59 (1) ◽  
pp. 1-16
Author(s):  
P. N. R. USHERWOOD
Keyword(s):  
Transmitter Release ◽  
Synaptic Vesicles ◽  
Schistocerca Gregaria ◽  
Spatial Arrangement ◽  
Muscle Fibres ◽  
Spontaneous Release ◽  
Axon Terminals ◽  
Synaptic Potentials ◽  
Nerve Muscle

1. When the motorneurones to the femoral part of the retractor unguis muscle of the locust Schistocerca gregaria are severed, the changes in impulse-linked release and spontaneous release of transmitter which take place at the synapses between the motorneurones and the retractor unguis muscle fibres can be related to known changes in the numbers and distribution of synaptic vesicles at these synapses. 2. Impulse-linked transmitter release fails when the synaptic vesicles aggregate to form clumps of vesicles, and at this time the miniature discharge recorded from the muscle fibres become characterized, initially, by bursts of miniature excitatory post-synaptic potentials (min. EPSPs) and, eventually, by ‘giant’ intracellular min. EPSPs up to 15 mV in amplitude. 3. The appearance of ‘giant’ potentials is accompanied by an overall fall in the frequency of the miniature discharge, which continues to decline thereafter until spontaneous transmitter release fails. The miniature discharge ceases at a time when the axon terminals are engulfed by glial tissue or become devoid of synaptic vesicles. 4. The parallel changes in temporal arrangement of min. EPSPs and spatial arrangement of synaptic vesicles seen during degeneration of locust nerve-muscle synapses provide further support for the ‘vesicle hypothesis’.

Structural and functional changes of frog neuromuscular junctions in high calcium solutions

1971 ◽  
Vol 178 (1053) ◽  
pp. 407-415 ◽  
Keyword(s):  
Transmitter Release ◽  
Synaptic Vesicles ◽  
Neuromuscular Junctions ◽  
Motor Nerve ◽  
Secretory Response ◽  
Spontaneous Release ◽  
Functional Changes ◽  
High Calcium ◽  
Release Of Acetylcholine ◽  
Evoked Transmitter Release

When frog muscles are exposed for several hours to a solution of isotonic calcium chloride, the secretory response of the motor nerve terminals to imposed depolarization ultimately fails and the rate of spontaneous release of acetylcholine also declines towards zero. The failure of depolarization-evoked transmitter release is irreversible while spontaneous release reappears, though in highly abnormal fashion, when the muscle is returned to a normal ionic medium. Examination of motor end-plates, during various stages of calcium treatment, shows that there is gradual intra-axonal agglutination of synaptic vesicles which is only very incompletely reversible. This effect is presumably the consequence of gradual entry and intracellular accumulation of calcium ions. Analogous treatment with isotonic magnesium, while resulting in immediate loss of evoked transmitter release, does not lead to progressive agglutination of synaptic vesicles, nor to irreversible impairment of the secretory response of the nerve terminal. The possible relations between structural and functional changes during calcium and magnesium treatment are discussed.

The Effect of Metabolic Inhibitors on the Cockroach Nerve-Muscle Synapse

1974 ◽  
Vol 61 (2) ◽  
pp. 331-343
Author(s):  
D. REES
Keyword(s):  
Synaptic Vesicle ◽  
White Muscle ◽  
Metabolic Inhibition ◽  
Metabolic Inhibitors ◽  
Muscle Fibres ◽  
Axon Terminals ◽  
Red Muscle ◽  
Electrophysiological Studies ◽  
Nerve Muscle

1. The application of metabolic inhibitors to nerve-muscle synapses on ‘white’ and ‘red’ fibres in the retractor unguis muscles of P. americana and B. giganteus resulted in a dramatic increase in the spontaneous miniature potential discharge and was accompanied by a summation of the miniature potentials to form ‘composite’ potentials. 2. Axon terminals associated with ‘white’ muscle fibres responded faster to metabolic inhibitors than those axon terminals associated with ‘red’ muscle fibres. 3. Correlated ultrastructural and electrophysiological studies inferred that a tentative relationship existed between the miniature potential activities and synaptic vesicle distributions of the nerve-muscle synapses during the phases of metabolic inhibition.

Role of Mitochondrial Dysfunction in the Ca2+-Induced Decline of Transmitter Release at K+-Depolarized Motor Neuron Terminals

1999 ◽  
Vol 81 (2) ◽  
pp. 498-506 ◽  
Author(s):  
Michelle A. Calupca ◽  
Gregory M. Hendricks ◽  
Jean C. Hardwick ◽  
Rodney L. Parsons
Keyword(s):  
Motor Neuron ◽  
Mitochondrial Dysfunction ◽  
Transmitter Release ◽  
Synaptic Vesicles ◽  
Prolonged Exposure ◽  
Nerve Terminals ◽  
Atp Production ◽  
Neuron Terminals ◽  
Nerve Muscle

Role of mitochondrial dysfunction in the Ca2+-induced decline of transmitter release at K+-depolarized motor neuron terminals. The present study tested whether a Ca2+-induced disruption of mitochondrial function was responsible for the decline in miniature endplate current (MEPC) frequency that occurs with nerve-muscle preparations maintained in a 35 mM potassium propionate (35 mM KP) solution containing elevated calcium. When the 35 mM KP contained control Ca2+(1 mM), the MEPC frequency increased and remained elevated for many hours, and the mitochondria within twitch motor neuron terminals were similar in appearance to those in unstimulated terminals. All nerve terminals accumulated FM1–43 when the dye was present for the final 6 min of a 300-min exposure to 35 mM KP with control Ca2+. In contrast, when Ca2+ was increased to 3.6 mM in the 35 mM KP solution, the MEPC frequency initially reached frequencies >350 s− 1 but then gradually fell approaching frequencies <50 s−1. A progressive swelling and eventual distortion of mitochondria within the twitch motor neuron terminals occurred during prolonged exposure to 35 mM KP with elevated Ca2+. After ∼300 min in 35 mM KP with elevated Ca2+, only 58% of the twitch terminals accumulated FM1–43. The decline in MEPC frequency in 35 mM KP with elevated Ca2+ was less when 15 mM glucose was present or when preparations were pretreated with 10 μM oligomycin and then bathed in the 35 mM KP with glucose. When glucose was present, with or without oligomycin pretreatment, a greater percentage of twitch terminals accumulated FM1–43. However, the mitochondria in these preparations were still greatly swollen and distorted. We propose that prolonged depolarization of twitch motor neuron terminals by 35 mM KP with elevated Ca2+ produced a Ca2+-induced decrease in mitochondrial ATP production. Under these conditions, the cytosolic ATP/ADP ratio was decreased thereby compromising both transmitter release and refilling of recycled synaptic vesicles. The addition of glucose stimulated glycolysis which contributed to the maintenance of required ATP levels.

scholarly journals Spontaneous Miniature Potentials in Denervated Coxal Muscle Fibres of the American Cockroach

1986 ◽  
Vol 120 (1) ◽  
pp. 143-151
Author(s):  
HIROSHI WASHIO
Keyword(s):  
Nerve Stimulation ◽  
American Cockroach ◽  
Muscle Fibres ◽  
Nerve Terminals ◽  
Distal Stump ◽  
Spontaneous Release ◽  
Nerve Section ◽  
Functional Changes ◽  
Nerve Muscle ◽  
Regenerating Nerve

1. Functional changes following denervation have been studied by intracellular recording at the neuromuscular junction of the cockroach coxal muscle. 2. Spontaneous subthreshold activity disappeared together with nerve-muscle transmission in about 2 days after nerve section at 26°C. The onset of the failure was mainly dependent on the temperature and also on the length of the transected distal stump. After complete cessation of the miniature excitatory postsynaptic potentials (MEPSPs) for about 3 weeks at 26°C, the miniature potentials resumed at a slower rate. Regeneration occurred faster when axotomy was performed by crushing the nerve rather than by sectioning. 3. Resumption of the MEPSPs was accompanied by response to nerve stimulation. However, hypertonic and hypotonic saline, and excess potassium, failed to increase the frequency of the resumed MEPSPs recorded between 15 and 45 days following denervation. 4. It is suggested that the resumed spontaneous release of transmitter may be derived from regenerating nerve terminals.

The Same Synaptic Vesicles Originate Synchronous and Asynchronous Transmitter Release

Acta Naturae ◽  
2015 ◽  
Vol 7 (3) ◽  
pp. 81-88 ◽  
Author(s):  
P. N. Grigoryev ◽  
A. L. Zefirov
Keyword(s):  
Synaptic Vesicle ◽  
High Frequency ◽  
Transmitter Release ◽  
Synaptic Vesicles ◽  
High Frequency Stimulation ◽  
Vesicle Pools ◽  
Bivalent Cations ◽  
Frequency Stimulation ◽  
Nerve Muscle ◽  
Vesicle Pool

Transmitter release and synaptic vesicle exo- and endocytosis during high-frequency stimulation (20 pulses/s) in the extracellular presence of different bivalent cations (Ca2+, Sr2+ or Ba2+) were studied in frog cutaneous pectoris nerve-muscle preparations. It was shown in electrophysiological experiments that almost only synchronous transmitter release was registered in a Ca2+-containing solution; a high intensity of both synchronous and asynchronous transmitter release was registered in a Sr2+-containing solution, and asynchronous transmitter release almost only was observed in a Ba2+-containing solution. It was shown in experiments with a FM 1-43 fluorescent dye that the synaptic vesicles that undergo exocytosis-endocytosis during synchronous transmitter release (Ca-solutions) are able to participate in asynchronous exocytosis in Ba-solutions. The vesicles that had participated in the asynchronous transmitter release (Ba-solutions) could subsequently participate in a synchronous release (Ca-solutions). It was shown in experiments with isolated staining of recycling and reserve synaptic vesicle pools that both types of evoked transmitter release originate from the same synaptic vesicle pool.

Real-time measurement of transmitter release from single synaptic vesicles

Nature ◽  
1995 ◽  
Vol 377 (6544) ◽  
pp. 62-65 ◽  
Author(s):  
Dieter Bruns ◽  
Reinhard Jahn
Keyword(s):  
Real Time ◽  
Transmitter Release ◽  
Synaptic Vesicles ◽  
Time Measurement ◽  
Real Time Measurement

The fate of foreign endplates in cross-innervated rat soleus muscle

1980 ◽  
Vol 208 (1171) ◽  
pp. 189-222 ◽  
Keyword(s):  
Muscle Fibre ◽  
Proximal Region ◽  
Presynaptic Terminal ◽  
Motor Axon ◽  
Muscle Fibres ◽  
Nerve Terminals ◽  
Axon Terminals ◽  
Adult Rat ◽  
Rat Soleus Muscle ◽  
Postsynaptic Site

After transplantation of the superficial fibular and the medial plantar nerve to neighbouring sites in the proximal region of adult rat soleus muscles many muscle fibres were initially innervated by axons in both foreign nerves after resection of the original soleus nerve. The foreign endplates were formed at ectopic sites and were often separately locatedon individual muscle fibres. After 3-4 weeks many endplates had been eliminated and most muscle fibres were innervated by only a single foreign axon. Many muscle fibres still had multiple esterase-staining endplate sites in the region innervated by the foreign nerve. On exami­nation by electronmicroscopy, some of these sites were seen to have lost their presynaptic terminal while the postsynaptic structure of the endplate remained intact. Other sites were only partially occupied by motor axon terminals. On each muscle fibre there was always at least one fully occupied endplate region. In some instances separate endplate sites on the same muscle fibre were innervated by branches of the same motor axon. We conclude that the elimination of endplates is due to a competitive interaction between motor axons innervating the same muscle fibre. Morphologically, the elimination of functional endplates is caused by a retraction of nerve terminals from the postsynaptic site.

Pharmacological Properties of Excitatory Neuromuscular Synapses in the Locust

1968 ◽  
Vol 49 (2) ◽  
pp. 341-361
Author(s):  
P. N. R. USHERWOOD ◽  
P. MACHILI
Keyword(s):  
Muscle Fibres ◽  
Amino Group ◽  
Mechanical Responses ◽  
Neuromuscular Synapses ◽  
Level Of Activity ◽  
Excitatory Activity ◽  
Wide Range ◽  
Nerve Muscle ◽  
Related Compounds ◽  
Stimulation Of

1. The effects of a wide range of amino acids and related compounds on retractor unguis nerve-muscle preparations from the locust, grasshopper and cockroach have been investigated. 2. L-glutamate is the most active excitatory substance. The presence of two acidic groups and one amino group is essential for excitatory activity while the position of the amino group is of some importance in determining the level of activity. 3. When L-glutamate is applied iontophoretically to the muscle fibres, ‘glutamate’ depolarizations are recorded only at the synaptic sites. Other evidence that the action of glutamate is restricted to the synaptic sites is presented. 4. Perfusion of isolated locust retractor unguis nerve-muscle preparations with locust haemolymph does not markedly affect the neurally evoked mechanical responses. It appears that locust haemolymph contains little ‘free’ L-glutamate. 5. Four acidic amino aids have been identified in the perfusate from isolated retractor unguis preparations namely, glycine, alanine, aspartate and L-glutamate. However, only L-glutamate increases in concentration during stimulation of the retractor unguis nerve.

Studies on Locust Neuromuscular Physiology in Relation to Glutamic Acid

1974 ◽  
Vol 60 (3) ◽  
pp. 673-705 ◽  
Author(s):  
A. N. CLEMENTS ◽  
TERRY E. MAY
Keyword(s):  
Amino Acids ◽  
Connective Tissue ◽  
Glutamic Acid ◽  
Diffusion Barrier ◽  
Muscle Fibres ◽  
Magnesium Ions ◽  
Calcium And Magnesium ◽  
Nerve Muscle ◽  
Connective Tissue Sheath ◽  
Calcium And Magnesium Ions

1. Two nerve-muscle preparations were used to investigate the physiology of the locust retractor unguis muscle in relation to L-glutamic acid. These were an ‘isolated preparation’, in which the muscle and its nerve were dissected out, and a ‘perfusedfemur preparation’, in which the muscle suffered no mechanical disturbance. 2. Exposure of the nerve--muscle preparations to glutamate caused a variety of responses, some of which were shown to be abnormal and due to the experimental conditions. 3. When locust femora were perfused with saline or haemolymph the retractor unguis muscles were much more severely affected by glutamate if the hydrostatic pressure was slightly raised. At raised pressures the perfused-femur preparations were particularly prone to give repetitive and spontaneous contractions. 4. Analysis of haemolymph from adult male locusts showed that it contained, on average, 0-2 mmol/1 L-glutamate, 45 mol/1 total non-peptide amino acids, 5-0 mmol/1 calcium, and 11-6 mmol/1 magnesium. It was calculated that approximately 50% of the calcium and 75% of the magnesium ions are bound to amino acids, and that approximately 25% of the glutamic acid is bound to divalent metal ions. 5. The isolated preparations were severely affected by glutamate at the concentration at which it occurs in haemolymph, and it was concluded that in the intact locust some mechanism must protect the neuromuscular synapses from haemolymphg lutamate. No evidence could be obtained of the sequestration of glutamate by haemocytes, or of binding of glutamate to haemolymph proteins. 6. Calcium and magnesium ions reduced the sensitivity of nerve-muscle preparations to glutamate to a greater extent than could be accounted for by the formation of amino acid-metal complexes. This suggests that the protection afforded by calcium and magnesium involves an interaction of the metal ions with the neuromuscular system itself. 7. The retractor unguis muscle was much less sensitive to glutamate when it was contained within an undissected femur than in an isolated preparation. It was concluded that the muscle is normally protected from haemolymph glutamate by a diffusion barrier which is damaged on dissection. 8. Comparison of the fine structure of retractor unguis muscles, fixed either after dissection or while still contained within the femur, showed that dissection normally caused a partial separation of muscle fibres and damage to the connective tissue sheath, with the resultant exposure of some nerve endings. The connective tissue sheath may constitute the postulated diffusion barrier. 9. The excitatory synapses of the locust retractor unguis muscle are believed to be isolated from haemolymph glutamate by a diffusion barrier, which is tentatively identified with the connective tissue sheath that binds the muscle fibres together. Calcium and magnesium ions reduce the sensitivity of nerve-muscle preparations to glutamate, and may have such a role in the living insect.

scholarly journals AXONAL AGRANULAR RETICULUM AND SYNAPTIC VESICLES IN CULTURED EMBRYONIC CHICK SYMPATHETIC NEURONS

1973 ◽  
Vol 57 (1) ◽  
pp. 88-108 ◽  
Author(s):  
Saul Teichberg ◽  
Eric Holtzman
Keyword(s):  
Synaptic Vesicles ◽  
Sympathetic Neurons ◽  
Size Spectrum ◽  
Embryonic Chick ◽  
Membrane Systems ◽  
Axon Terminals ◽  
Golgi Membranes ◽  
Storage Vesicles ◽  
Adrenergic Systems ◽  
Catecholamine Storage

Cultured chick embryonic sympathetic neurons contain an extensive axonal network of sacs and tubules of agranular reticulum. The reticulum is also seen branching into networks in axon terminals and varicosities. The axonal reticulum and perikaryal endoplasmic reticulum resemble one another in their content of cytochemically demonstrable enzyme activities (G6Pase and IDPase) and in their characteristic membrane thicknesses (narrower than plasma membrane or some Golgi membranes). From the reticulum, both along the axon and at terminals, there appear to form dense-cored vesicles ranging in size from 400 to 1,000 Å in diameter. These vesicles behave pharmacologically and cytochemically like the classes of large and small catecholamine storage vesicles found in several adrenergic systems; for example, they can accumulate exogenous 5-hydroxydopamine. In addition, dense-cored vesicles at the larger (1,000 Å) end of the size spectrum appear to arise within perikaryal membrane systems associated with the Golgi apparatus; this is true also of very large (800–3,500 Å) dense-cored vesicles found in some perikarya.

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