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1. Acetylcholine (ACh) release from enzymatically exposed frog motor nerve terminals has been measured directly with closely apposed outside-out clamped patches of Xenopus myocyte membrane, rich in ACh receptor channels. When placed close to the synaptic surface of the terminal, such a membrane patch detects both nerve-evoked patch currents (EPCs) and spontaneous quantal 'miniature' patch currents (MPCs), from a few micrometres length of the terminal, in response to ACh release from the nearest three to five active zones. 2. Chemical measurements of ACh efflux from whole preparations revealed a spontaneous release rate of 4.1 pmol (2 h)-1, and no significant difference in resting efflux between enzyme-treated and control preparations. The ratio of enzyme-treated to contralateral control muscle efflux averaged 1.17, indicating that enzyme treatment did not affect spontaneous ACh release. Vesamicol (1.7 microM), which blocks the ACh transporter in synaptic vesicles, decreased the spontaneous release of ACh to 67% of control. 3. In the absence of nerve stimulation, the frequency of single-channel openings recorded by outside-out patch probes adjacent to nerve terminals was very low (1-2 min-1), and little different at a distance of hundreds of micrometres, suggesting that if ACh was continually leaking from the terminal in a non-quantal fashion, the amount being released near active zone regions on the terminal was below the limit of detection with the patches. 4. Direct measurements of the sensitivity of the patches, coupled with calculated ACh flux rates, lead to the conclusion that the amount of ACh released non-quantally from the synaptic surface of the frog nerve terminal is less than one-tenth the amount expected if all non-quantal release is from this region of the terminal membrane. 5. Following a series of single nerve shocks or a 50 Hz train of nerve stimuli, the frequency of asynchronous single-channel openings increased for several seconds. This transient increase in channel openings was not sensitive to movement of the patch electrode a significant distance (4 microns) away from the active sites, or to manipulations previously reported to block non-quantal transmitter leakage, including addition of 10 mM-Ca2+ or 1.7 microM-vesamicol to the bath. These channel openings appear to be due to an accumulation of ACh which originated from many evoked quanta, and not the effect of locally increased non-quantal ACh release due to nerve stimulation. 6. We conclude that transmitter leakage at adult frog terminals is either localized to a source other than the synaptic surface of the nerve terminal, or released in a widespread and diffuse fashion from many sources, which may include the nerve terminal.
Anderson,
Pharmacological characterization of the acetylcholine transport system in purified Torpedo electric organ synaptic vesicles.
1983, Pubmed
Anderson,
Pharmacological characterization of the acetylcholine transport system in purified Torpedo electric organ synaptic vesicles.
1983,
Pubmed
Anderson,
Voltage clamp analysis of acetylcholine produced end-plate current fluctuations at frog neuromuscular junction.
1973,
Pubmed
Anderson,
Effects of innervation on the distribution of acetylcholine receptors on cultured muscle cells.
1977,
Pubmed
,
Xenbase
Betz,
Effects of proteolytic enzymes on function and structure of frog neuromuscular junctions.
1973,
Pubmed
Bray,
Evidence for the role of non-quantal acetylcholine in the maintenance of the membrane potential of rat skeletal muscle.
1982,
Pubmed
D'Alonzo,
Profiles of evoked release along the length of frog motor nerve terminals.
1985,
Pubmed
Dennis,
Electrically induced release of acetylcholine from denervated Schwann cells.
1974,
Pubmed
Desaki,
The overall morphology of neuromuscular junctions as revealed by scanning electron microscopy.
1981,
Pubmed
Drachman,
Neurotrophic regulation of two properties of skeletal muscle by impulse-dependent and spontaneous acetylcholine transmission.
1982,
Pubmed
Edwards,
Is an acetylcholine transport system responsible for nonquantal release of acetylcholine at the rodent myoneural junction?
1985,
Pubmed
Edwards,
A possible role for the acetylcholine transport system in non-quantal release of acetylcholine at the rodent myoneural junction.
1988,
Pubmed
Gage,
Miniature end-plate currents and potentials generated by quanta of acetylcholine in glycerol-treated toad sartorius fibres.
1972,
Pubmed
Glavinović,
Variability of quantal events in control solution and after cholinesterase blockade in frog.
1986,
Pubmed
Heuser,
Evidence for recycling of synaptic vesicle membrane during transmitter release at the frog neuromuscular junction.
1973,
Pubmed
Heuser,
Structural changes after transmitter release at the frog neuromuscular junction.
1981,
Pubmed
Hume,
Acetylcholine release from growth cones detected with patches of acetylcholine receptor-rich membranes.
,
Pubmed
Jenden,
Simultaneous measurement of endogenous and deuterium-labeled tracer variants of choline and acetylcholine in subpicomole quantities by gas chromatography-mass spectrometry.
1973,
Pubmed
Katz,
Transmitter leakage from motor nerve endings.
1977,
Pubmed
Katz,
Does the motor nerve impulse evoke 'non-quantal' transmitter release?
1981,
Pubmed
KATZ,
PROPAGATION OF ELECTRIC ACTIVITY IN MOTOR NERVE TERMINALS.
1965,
Pubmed
Kidokoro,
Distribution and density of alpha-bungarotoxin binding sites on innervated and noninnervated Xenopus muscle cells in culture.
1982,
Pubmed
,
Xenbase
Ko,
A lectin, peanut agglutinin, as a probe for the extracellular matrix in living neuromuscular junctions.
1987,
Pubmed
Kuffler,
The distribution of acetylcholine sensitivity at the post-synaptic membrane of vertebrate skeletal twitch muscles: iontophoretic mapping in the micron range.
1975,
Pubmed
Kuffler,
The number of transmitter molecules in a quantum: an estimate from iontophoretic application of acetylcholine at the neuromuscular synapse.
1975,
Pubmed
Letinsky,
Histological staining of pre- and postsynaptic components of amphibian neuromuscular junctions.
1980,
Pubmed
Lev-Tov,
A study of tetanic and post-tetanic potentiation of miniature end-plate potentials at the frog neuromuscular junction.
1980,
Pubmed
Mathers,
Studies on neurotrophic regulation of murine skeletal muscle.
1978,
Pubmed
Miledi,
The effect of lanthanum ions on acetylcholine in frog muscle.
1980,
Pubmed
Miller,
Endocytosis of synaptic vesicle membrane at the frog neuromuscular junction.
1984,
Pubmed
Mitchell,
The spontaneous release of acetylcholine from the denervated hemidiaphragm of the rat.
1963,
Pubmed
Molenaar,
Surplus acetylcholine and acetylcholine release in the rat diaphragm.
1987,
Pubmed
Neher,
Discrete changes of cell membrane capacitance observed under conditions of enhanced secretion in bovine adrenal chromaffin cells.
1982,
Pubmed
OGSTON,
Removal of acetylcholine from a limited volume by diffusion.
1955,
Pubmed
Pestronk,
Cholinergic transmission regulates extrajunctional acetylcholine receptors.
1980,
Pubmed
Spitzer,
The development of the action potential mechanism of amphibian neurons isolated in culture.
1976,
Pubmed
,
Xenbase
Stanley,
The effects of nerve section on the non-quantal release of ACh from the motor nerve terminal.
1986,
Pubmed
Sun,
Non-quantal release of acetylcholine at a developing neuromuscular synapse in culture.
1985,
Pubmed
,
Xenbase
Vyskocil,
Non-quantal release of transmitter at mouse neuromuscular junction and its dependence on the activity of Na+-K+ ATP-ase.
1977,
Pubmed
Vyskocil,
An analysis of the mechanisms underlying the non-quantal release of acetylcholine at the mouse neuromuscular junction.
1983,
Pubmed
Young,
Spontaneous release of transmitter from growth cones of embryonic neurones.
,
Pubmed
,
Xenbase
