Biomaterial Database

A new method for determining co-operativity in neurotransmitter release. 1986

H Parnas, and I Parnas, and L Segel

It has been accepted for some time that neurotransmitter release exhibits a co-operative dependence on calcium. Here we suggest a new procedure for estimating the co-operativity, based on the early rise of synaptic delay histograms of induced release at low quantal content. Measurements of such histograms at the lobster neuromuscular junction are reported. On the basis of this data, and also of data from the literature for other species, a re-examination is made of the conventional hypothesis that the kinetics of release is primarily determined by the time course of entry and removal of calcium ions. Two major new hypotheses for the nature of co-operativity are discussed, both containing the additional feature that membrane depolarization activates a molecule or complex that only then can bind calcium and induce release. The measurements confirm the hypothesis that the co-operativity arises from the action of several complexes between calcium and a depolarization-activated molecule to initiate the release of a vesicle. The co-operativity exponent is estimated to be between three and five in lobster neuromuscular junction and also in crayfish, macrobrachium, and frog.

UI	MeSH Term	Description	Entries
D007700	Kinetics	The rate dynamics in chemical or physical systems.
D008121	Nephropidae	Family of large marine CRUSTACEA, in the order DECAPODA. These are called clawed lobsters because they bear pincers on the first three pairs of legs. The American lobster and Cape lobster in the genus Homarus are commonly used for food.	Clawed Lobsters,Homaridae,Homarus,Lobsters, Clawed,Clawed Lobster,Lobster, Clawed
D008433	Mathematics	The deductive study of shape, quantity, and dependence. (From McGraw-Hill Dictionary of Scientific and Technical Terms, 6th ed)	Mathematic
D008954	Models, Biological	Theoretical representations that simulate the behavior or activity of biological processes or diseases. For disease models in living animals, DISEASE MODELS, ANIMAL is available. Biological models include the use of mathematical equations, computers, and other electronic equipment.	Biological Model,Biological Models,Model, Biological,Models, Biologic,Biologic Model,Biologic Models,Model, Biologic
D009132	Muscles	Contractile tissue that produces movement in animals.	Muscle Tissue,Muscle,Muscle Tissues,Tissue, Muscle,Tissues, Muscle
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
D000494	Allosteric Regulation	The modification of the reactivity of ENZYMES by the binding of effectors to sites (ALLOSTERIC SITES) on the enzymes other than the substrate BINDING SITES.	Regulation, Allosteric,Allosteric Regulations,Regulations, Allosteric
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
D018377	Neurotransmitter Agents	Substances used for their pharmacological actions on any aspect of neurotransmitter systems. Neurotransmitter agents include agonists, antagonists, degradation inhibitors, uptake inhibitors, depleters, precursors, and modulators of receptor function.	Nerve Transmitter Substance,Neurohormone,Neurohumor,Neurotransmitter Agent,Nerve Transmitter Substances,Neurohormones,Neurohumors,Neuromodulator,Neuromodulators,Neuroregulator,Neuroregulators,Neurotransmitter,Neurotransmitters,Substances, Nerve Transmitter,Transmitter Substances, Nerve,Substance, Nerve Transmitter,Transmitter Substance, Nerve