Biomaterial Database

Effects of permeant monovalent cations on end-plate channels. 1979

P W Gage, and D Van Helden

1. The time constant of decay (tau D) and peak amplitude of miniature end-plate currents (m.e.p.c.s) were recorded in voltage-clamped toad sartorius fibres. The conductance (gamma) and average lifetime (tau N) of end-plate channels activated by ionophoretically applied acetylcholine were calculated from records of current fluctuations and null potentials recorded in the same fibres. tau D was significantly greater than tau N measured at the same end-plate. 2. Substitution for LiCl for NaCl increased tau D and tau N but decreased gamma and the peak amplitude of m.e.p.c.s. In contrast substitution of CsCl for NaCl decreased tau D and tau N but increased gamma and the peak amplitude of m.e.p.c.s. 3. In normal (Na) solution and in solutions in which Na had been replaced with Li, Cs and K, the ratios of average decay time constants of m.e.p.c.s and average channel lifetimes followed the sequence (tau(Li) greater than tau(Na) greater than tau(Cs) greater than tau(K)). 4. Substitution of Li, Cs or K for Na had little effect on the acetylcholine null potential. Average null potentials in Li, Na and Cs solutions were -6.1, -3.2 and 0.1 mV at 20 degrees C, and -7.3, -5.3 and -0.1 mV at 8 degrees C, respectively. The average null potential in K solution measured at 8 degrees C was -2.4 mV. 5. Peak conductance during an m.e.p.c. (Gp) followed the sequence (Gp(K) greater than or equal to Gp(Cs) greater than Gp(Na) greater than Gp(Li)). Single channel conductance followed a similar sequence of gamma(K) greater than or equal to gamma(Cs) greater than gamma(Na) greater than gamma(Li). 6. The voltage sensitivity of the rate of decay of m.e.p.c.s and of average channel lifetime was affected by substituting monovalent cations for Na, being greater in Li solution and less in Cs or K solutions. The total amount of charge moving across a single channel or across channels activated during an m.e.p.c. was largely unchanged in Li, Na, Cs and K solutions. 7. Single channel conductance and peak conductance during an m.e.p.c. varied with membrane potential in normal (Na) solution, decreasing with membrane hyperpolarization. This effect was more marked in Li solution but was less evident in Cs or K solutions.

UI	MeSH Term	Description	Entries
D007473	Ion Channels	Gated, ion-selective glycoproteins that traverse membranes. The stimulus for ION CHANNEL GATING can be due to a variety of stimuli such as LIGANDS, a TRANSMEMBRANE POTENTIAL DIFFERENCE, mechanical deformation or through INTRACELLULAR SIGNALING PEPTIDES AND PROTEINS.	Membrane Channels,Ion Channel,Ionic Channel,Ionic Channels,Membrane Channel,Channel, Ion,Channel, Ionic,Channel, Membrane,Channels, Ion,Channels, Ionic,Channels, Membrane
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
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
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
D009132	Muscles	Contractile tissue that produces movement in animals.	Muscle Tissue,Muscle,Muscle Tissues,Tissue, Muscle,Tissues, Muscle
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
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.
D002024	Bufo marinus	A species of the true toads, Bufonidae, becoming fairly common in the southern United States and almost pantropical. The secretions from the skin glands of this species are very toxic to animals.	Rhinella marina,Toad, Giant,Toad, Marine,Giant Toad,Giant Toads,Marine Toad,Marine Toads,Toads, Giant,Toads, Marine
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
D002586	Cesium	A member of the alkali metals. It has an atomic symbol Cs, atomic number 55, and atomic weight 132.91. Cesium has many industrial applications, including the construction of atomic clocks based on its atomic vibrational frequency.	Caesium,Caesium-133,Cesium-133,Caesium 133,Cesium 133