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Membrane currents and cholinergic regulation of K+ current in esophageal smooth muscle cells. 1990

S M Sims, and M B Vivaudou, and C Hillemeier, and P Biancani, and J V Walsh, and J J Singer
Department of Physiology, University of Massachusetts Medical School, Worcester 01655.

The tight-seal whole cell recording technique with patch pipettes was used to study membrane currents of smooth muscle cells freshly dissociated from the esophagus of cats. Under voltage clamp with K+ in the pipette, depolarizing commands elicited an initial inward current followed by a transient outward current that peaked and then declined to reveal spontaneous outward currents (SOCs). SOCs were evident at -60 mV and more positive potentials. The reversal of SOCs at the K+ equilibrium potential and their suppression by tetraethylammonium chloride lead to the conclusion that they represent the activity of K+ channels. Acetylcholine (ACh) caused reversible contraction of these cells and had two successive effects on membrane currents, causing transient activation of K+ current followed by suppression of SOCs. Both of these effects were blocked by atropine. Consistent with these observations, in current clamp, ACh caused a transient hyperpolarization followed by depolarization. The inward current activated by depolarization was blocked by external Cd2+, consistent with the inward current being a voltage-activated calcium current. Two types of Ca2+ current could be distinguished on the basis of voltage-activation range, time course of inactivation and "run-down" during whole cell recording.

UI MeSH Term Description Entries
D007700 Kinetics The rate dynamics in chemical or physical systems.
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
D009116 Muscarine A toxic alkaloid found in Amanita muscaria (fly fungus) and other fungi of the Inocybe species. It is the first parasympathomimetic substance ever studied and causes profound parasympathetic activation that may end in convulsions and death. The specific antidote is atropine.
D009119 Muscle Contraction A process leading to shortening and/or development of tension in muscle tissue. Muscle contraction occurs by a sliding filament mechanism whereby actin filaments slide inward among the myosin filaments. Inotropism,Muscular Contraction,Contraction, Muscle,Contraction, Muscular,Contractions, Muscle,Contractions, Muscular,Inotropisms,Muscle Contractions,Muscular Contractions
D009130 Muscle, Smooth Unstriated and unstriped muscle, one of the muscles of the internal organs, blood vessels, hair follicles, etc. Contractile elements are elongated, usually spindle-shaped cells with centrally located nuclei. Smooth muscle fibers are bound together into sheets or bundles by reticular fibers and frequently elastic nets are also abundant. (From Stedman, 25th ed) Muscle, Involuntary,Smooth Muscle,Involuntary Muscle,Involuntary Muscles,Muscles, Involuntary,Muscles, Smooth,Smooth Muscles
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.
D002104 Cadmium An element with atomic symbol Cd, atomic number 48, and atomic weight 112.41. It is a metal and ingestion will lead to CADMIUM POISONING.
D002415 Cats The domestic cat, Felis catus, of the carnivore family FELIDAE, comprising over 30 different breeds. The domestic cat is descended primarily from the wild cat of Africa and extreme southwestern Asia. Though probably present in towns in Palestine as long ago as 7000 years, actual domestication occurred in Egypt about 4000 years ago. (From Walker's Mammals of the World, 6th ed, p801) Felis catus,Felis domesticus,Domestic Cats,Felis domestica,Felis sylvestris catus,Cat,Cat, Domestic,Cats, Domestic,Domestic Cat
D002478 Cells, Cultured Cells propagated in vitro in special media conducive to their growth. Cultured cells are used to study developmental, morphologic, metabolic, physiologic, and genetic processes, among others. Cultured Cells,Cell, Cultured,Cultured Cell
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.

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