Biomaterial Database

The calcium dependence of spontaneous and evoked quantal release at the frog neuromuscular junction. 1983

S B Barton, and I S Cohen, and W van der Kloot

1. The quantal output from stimulated nerve terminals in the frog sciatic nerve-sartorius muscle preparation in low-Ca(2+) Ringer solution was measured by the coefficient of variation and the failures methods. Adding sucrose to the Ringer to increase the tonicity or adding ethanol increased miniature end-plate potential (m.e.p.p.) frequency and also the end-plate potential (e.p.p.) amplitude. Earlier reports suggested that increases in tonicity did not increase evoked quantal release.2. Concanavalin A has been reported to block the increase in m.e.p.p. frequency caused by increasing the tonicity of the Ringer (Gorio & Mauro, 1979). This effect was confirmed. The lectin-treated preparations also failed to show an increase in evoked quantal release when the tonicity was increased.3. A model in which both spontaneous and evoked quantal releases depend on some power of the intracellular [Ca(2+)] is presented. The model predicts that rises in m.e.p.p. frequency will be accompanied by increased quantal output from stimulated nerve terminals. The maximum slope of the relationship between log (evoked quantal output) and log ([Ca(2+)](out)) will be less than the true power. A theoretical analysis shows that, as the true power approaches infinity, the maximum slope will be slightly above 4. The value for the slope usually found experimentally at the frog neuromuscular junction is also about 4.4. The model does not fit the experimental data. The observed increases in evoked quantal release are higher than those predicted for the observed increases in spontaneous release. There are several possible explanations for the discrepancy. Treatments that increase m.e.p.p. frequency may also increase Ca(2+) influx into the stimulated terminal. However, we prefer the explanation that there is a fraction of spontaneous release that is independent of the [Ca(2+)] in the terminal; if this is true the model might account for the data.5. The model can account for a variety of puzzling experimental observations, including: (a) the effect of hypertonic solutions and of diamine in decreasing the slope in the relation between log (evoked quantal output) and log ([Ca(2+)](out)); (b) the slope of near 1 observed at the crustacean neuromuscular junction; (c) the decrease in the slope produced by treatment with botulinum toxin.

UI	MeSH Term	Description	Entries
D006982	Hypertonic Solutions	Solutions that have a greater osmotic pressure than a reference solution such as blood, plasma, or interstitial fluid.	Hypertonic Solution,Solution, Hypertonic,Solutions, Hypertonic
D008959	Models, Neurological	Theoretical representations that simulate the behavior or activity of the neurological system, processes or phenomena; includes the use of mathematical equations, computers, and other electronic equipment.	Neurologic Models,Model, Neurological,Neurologic Model,Neurological Model,Neurological Models,Model, Neurologic,Models, Neurologic
D009045	Motor Endplate	The specialized postsynaptic region of a muscle cell. The motor endplate is immediately across the synaptic cleft from the presynaptic axon terminal. Among its anatomical specializations are junctional folds which harbor a high density of cholinergic receptors.	Motor End-Plate,End-Plate, Motor,End-Plates, Motor,Endplate, Motor,Endplates, Motor,Motor End Plate,Motor End-Plates,Motor Endplates
D009469	Neuromuscular Junction	The synapse between a neuron and a muscle.	Myoneural Junction,Nerve-Muscle Preparation,Junction, Myoneural,Junction, Neuromuscular,Junctions, Myoneural,Junctions, Neuromuscular,Myoneural Junctions,Nerve Muscle Preparation,Nerve-Muscle Preparations,Neuromuscular Junctions,Preparation, Nerve-Muscle,Preparations, Nerve-Muscle
D011894	Rana pipiens	A highly variable species of the family Ranidae in Canada, the United States and Central America. It is the most widely used Anuran in biomedical research.	Frog, Leopard,Leopard Frog,Lithobates pipiens,Frogs, Leopard,Leopard Frogs
D002118	Calcium	A basic element found in nearly all tissues. It is a member of the alkaline earth family of metals with the atomic symbol Ca, atomic number 20, and atomic weight 40. Calcium is the most abundant mineral in the body and combines with phosphorus to form calcium phosphate in the bones and teeth. It is essential for the normal functioning of nerves and muscles and plays a role in blood coagulation (as factor IV) and in many enzymatic processes.	Coagulation Factor IV,Factor IV,Blood Coagulation Factor IV,Calcium-40,Calcium 40,Factor IV, Coagulation
D003208	Concanavalin A	A MANNOSE/GLUCOSE binding lectin isolated from the jack bean (Canavalia ensiformis). It is a potent mitogen used to stimulate cell proliferation in lymphocytes, primarily T-lymphocyte, cultures.
D000200	Action Potentials	Abrupt changes in the membrane potential that sweep along the CELL MEMBRANE of excitable cells in response to excitation stimuli.	Spike Potentials,Nerve Impulses,Action Potential,Impulse, Nerve,Impulses, Nerve,Nerve Impulse,Potential, Action,Potential, Spike,Potentials, Action,Potentials, Spike,Spike Potential
D000818	Animals	Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA.	Animal,Metazoa,Animalia
D066298	In Vitro Techniques	Methods to study reactions or processes taking place in an artificial environment outside the living organism.	In Vitro Test,In Vitro Testing,In Vitro Tests,In Vitro as Topic,In Vitro,In Vitro Technique,In Vitro Testings,Technique, In Vitro,Techniques, In Vitro,Test, In Vitro,Testing, In Vitro,Testings, In Vitro,Tests, In Vitro,Vitro Testing, In