Biomaterial Database

Interaction of monovalent cations with tetrodotoxin and saxitoxin binding at sodium channels of frog myelinated nerve. 1990

U Lönnendonker, and B Neumcke, and R Stämpfli

I. Physiologisches Institut der Universität des Saarlandes, Hamburg, Federal Republic of Germany.

Na currents and Na-current fluctuations were measured in myelinated frog nerve fibres to study interactions between monovalent externally applied cations and the binding of the Na-channel blockers tetrodotoxin (TTX) or saxitoxin (STX). Adding 110 mM NaCl to Ringer's solution increased the maximum peak Na conductance by a factor of 2.51 in the presence of 12 nM TTX and by a factor of 2.43 in the presence of 4 nM STX. According to the analysis of Na-current fluctuations this increase of the Na conductance is mainly caused by an increase of the number N of unblocked Na channels per node, while the conductance of a single channel saturates in the hyperosmolar solutions. The increase of N is interpreted by displacement of TTX or STX from Na channels by external Na+. Relief of TTX blockage was also observed by adding 110 mM chloride salts of Li+, hydrazine+, guanidine+ and K+ to Ringer, but not in Ringer + 110 mM tetramethylammonium chloride or 250 mM sucrose. The increase of N by the external cations is a saturating function of the permeability of the Na channel to these ions. The results are interpreted by a toxin receptor in a superficial prefilter to the Na channel, which contributes to cation discrimination at the outer channel region.

UI	MeSH Term	Description	Entries
D008094	Lithium	An element in the alkali metals family. It has the atomic symbol Li, atomic number 3, and atomic weight [6.938; 6.997]. Salts of lithium are used in treating BIPOLAR DISORDER.	Lithium-7,Lithium 7
D009186	Myelin Sheath	The lipid-rich sheath surrounding AXONS in both the CENTRAL NERVOUS SYSTEMS and PERIPHERAL NERVOUS SYSTEM. The myelin sheath is an electrical insulator and allows faster and more energetically efficient conduction of impulses. The sheath is formed by the cell membranes of glial cells (SCHWANN CELLS in the peripheral and OLIGODENDROGLIA in the central nervous system). Deterioration of the sheath in DEMYELINATING DISEASES is a serious clinical problem.	Myelin,Myelin Sheaths,Sheath, Myelin,Sheaths, Myelin
D009412	Nerve Fibers	Slender processes of NEURONS, including the AXONS and their glial envelopes (MYELIN SHEATH). Nerve fibers conduct nerve impulses to and from the CENTRAL NERVOUS SYSTEM.	Cerebellar Mossy Fibers,Mossy Fibers, Cerebellar,Cerebellar Mossy Fiber,Mossy Fiber, Cerebellar,Nerve Fiber
D009994	Osmolar Concentration	The concentration of osmotically active particles in solution expressed in terms of osmoles of solute per liter of solution. Osmolality is expressed in terms of osmoles of solute per kilogram of solvent.	Ionic Strength,Osmolality,Osmolarity,Concentration, Osmolar,Concentrations, Osmolar,Ionic Strengths,Osmolalities,Osmolar Concentrations,Osmolarities,Strength, Ionic,Strengths, Ionic
D011188	Potassium	An element in the alkali group of metals with an atomic symbol K, atomic number 19, and atomic weight 39.10. It is the chief cation in the intracellular fluid of muscle and other cells. Potassium ion is a strong electrolyte that plays a significant role in the regulation of fluid volume and maintenance of the WATER-ELECTROLYTE BALANCE.
D011485	Protein Binding	The process in which substances, either endogenous or exogenous, bind to proteins, peptides, enzymes, protein precursors, or allied compounds. Specific protein-binding measures are often used as assays in diagnostic assessments.	Plasma Protein Binding Capacity,Binding, Protein
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
D002414	Cations, Monovalent	Positively charged atoms, radicals or group of atoms with a valence of plus 1, which travel to the cathode or negative pole during electrolysis.	Monovalent Cation,Cation, Monovalent,Monovalent Cations
D004553	Electric Conductivity	The ability of a substrate to allow the passage of ELECTRONS.	Electrical Conductivity,Conductivity, Electric,Conductivity, Electrical
D006834	Hydrazines	Substituted derivatives of hydrazine (formula H2N-NH2).	Hydrazide