Biomaterial Database

Voltage and temperature dependence of normal and chemically modified inactivation of sodium channels. Quantitative description by a cyclic three-state model. 1989

J Schmidtmayer

Physiologisches Institut der Universität Kiel, Federal Republic of Germany.

(1) Voltage clamp experiments were done on single myelinated nerve fibres of the frog, Rana esculenta, with 10 mM TEA in the external solution to block potassium channels. (2) The potential dependence of normal sodium current inactivation was studied over a potential range of V = -50 mV to 80 mV. At depolarizations (V greater than or equal to 30 mV) inactivation is diphasic. The relative contribution of the fast phase increases from 0.4 at V = 30 mV to 0.96 at V = 80 mV. At resting potential (V = 0 mV) recovery from inactivation shows a sigmoidal time course. At strong hyperpolarization (V = -50 mV) recovery is diphasic with a predominant fast phase. (3) For a quantitative description of these findings a cyclic three-state model of inactivation, with one open and two closed states, is formulated. The potential dependence of the rate constants is determined and calculations from this model are compared with the experimental data. (4) To test the availability of the proposed model, normal inactivation was modified by treatment with 0.6 mM chloramine-T. This substance causes inactivation to become slow and incomplete; the potential dependence of steady-state inactivation becomes non-monotonic. All these effects are explained as quantitative changes of the rate constants in the cyclic inactivation model. (5) The influence of temperature on normal inactivation was studied at a range of 8-20 C. Both time constants as well as the two inactivation components are temperature-dependent. For a quantitative description of temperature effects by the cyclic model, the activation enthalpies of the rate constants are evaluated.(ABSTRACT TRUNCATED AT 250 WORDS)

UI	MeSH Term	Description	Entries
D008564	Membrane Potentials	The voltage differences across a membrane. For cellular membranes they are computed by subtracting the voltage measured outside the membrane from the voltage measured inside the membrane. They result from differences of inside versus outside concentration of potassium, sodium, chloride, and other ions across cells' or ORGANELLES membranes. For excitable cells, the resting membrane potentials range between -30 and -100 millivolts. Physical, chemical, or electrical stimuli can make a membrane potential more negative (hyperpolarization), or less negative (depolarization).	Resting Potentials,Transmembrane Potentials,Delta Psi,Resting Membrane Potential,Transmembrane Electrical Potential Difference,Transmembrane Potential Difference,Difference, Transmembrane Potential,Differences, Transmembrane Potential,Membrane Potential,Membrane Potential, Resting,Membrane Potentials, Resting,Potential Difference, Transmembrane,Potential Differences, Transmembrane,Potential, Membrane,Potential, Resting,Potential, Transmembrane,Potentials, Membrane,Potentials, Resting,Potentials, Transmembrane,Resting Membrane Potentials,Resting Potential,Transmembrane Potential,Transmembrane Potential Differences
D009413	Nerve Fibers, Myelinated	A class of nerve fibers as defined by their structure, specifically the nerve sheath arrangement. The AXONS of the myelinated nerve fibers are completely encased in a MYELIN SHEATH. They are fibers of relatively large and varied diameters. Their NEURAL CONDUCTION rates are faster than those of the unmyelinated nerve fibers (NERVE FIBERS, UNMYELINATED). Myelinated nerve fibers are present in somatic and autonomic nerves.	A Fibers,B Fibers,Fiber, Myelinated Nerve,Fibers, Myelinated Nerve,Myelinated Nerve Fiber,Myelinated Nerve Fibers,Nerve Fiber, Myelinated
D011893	Rana esculenta	An edible species of the family Ranidae, occurring in Europe and used extensively in biomedical research. Commonly referred to as "edible frog".	Pelophylax esculentus
D002462	Cell Membrane	The lipid- and protein-containing, selectively permeable membrane that surrounds the cytoplasm in prokaryotic and eukaryotic cells.	Plasma Membrane,Cytoplasmic Membrane,Cell Membranes,Cytoplasmic Membranes,Membrane, Cell,Membrane, Cytoplasmic,Membrane, Plasma,Membranes, Cell,Membranes, Cytoplasmic,Membranes, Plasma,Plasma Membranes
D002463	Cell Membrane Permeability	A quality of cell membranes which permits the passage of solvents and solutes into and out of cells.	Permeability, Cell Membrane
D002700	Chloramines	Inorganic derivatives of ammonia by substitution of one or more hydrogen atoms with chlorine atoms or organic compounds with the general formulas R2NCl and RNCl2 (where R is an organic group).	Chloroamines
D004553	Electric Conductivity	The ability of a substrate to allow the passage of ELECTRONS.	Electrical Conductivity,Conductivity, Electric,Conductivity, Electrical
D004558	Electric Stimulation	Use of electric potential or currents to elicit biological responses.	Stimulation, Electric,Electrical Stimulation,Electric Stimulations,Electrical Stimulations,Stimulation, Electrical,Stimulations, Electric,Stimulations, Electrical
D004594	Electrophysiology	The study of the generation and behavior of electrical charges in living organisms particularly the nervous system and the effects of electricity on living organisms.
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