Biomaterial Database

Nitric oxide modulation of calcium-activated potassium channels in postganglionic neurones of avian cultured ciliary ganglia. 1993

M Cetiner, and M R Bennett

Department of Physiology, University of Sydney, N.S.W., Australia.

1. A study has been made of the modulation of calcium-activated potassium channels in cultured neurones of avian ciliary ganglia by sodium nitroprusside and L-arginine. 2. Sodium nitroprusside (100 microM) reduced the net outward current by 22 +/- 1% at 4.8 ms (mean +/- s.e. mean) and 25 +/- 1% at 350 ms during a test depolarization to +40 mV from a holding potential of -40 mV. The outward current remained reduced for the duration of the recording following a single application of sodium nitroprusside. These effects did not occur if the influx of calcium ions was first blocked with Cd2+ (500 microM). Application of ferrocyanide (100 microM) reduced the net outward current by only 6 +/- 3% at 350 ms during a test depolarization to +40 mV. 3. L-Arginine (270 microM) reduced the net outward current on average by 19 +/- 2% at 4.8 ms and 22 +/- 2% at 350 ms during a test depolarization to +40 mV. The current remained in this reduced state for the duration of the recording following a single application of L-arginine. These effects were reduced to 11 +/- 1% at 4.8 ms and 11 +/- 2% at 350 ms in the presence of N omega-nitro-L-arginine methyl ester (L-NAME, 100 microM). 4. In order to alleviate the dependence of calcium-activated potassium channels (Ik(Ca)) on the inward flux of calcium ions, the patch-clamp pipettes were filled with a solution containing 100 microM CaCl2, and the Ca2+ in the bathing solution was replaced with EGTA. Under these conditions sodium nitroprusside reduced the total outward current during a depolarizing pulse of + 40 mV by 9 +/_ 1% at 4.8 ms and by 36 +/- 3% at 350 ms. L-Arginine (270 microM) reduced this current under the same conditions by 9 +/- 1% at 4.8 ms and by 35 +/- 2% at 350 ms.5. Calcium-activated potassium currents were sensitive to apamin (50 nM), as this reduced the outward current by 23 +/- 3% at 350 ms when a high calcium-containing pipette was used during a depolarizing command to + 40 mV. L-Arginine still decreased the outward current in the presence of apamin(50 nM), by 5 +/- 1% at 4.8 ms and by 19 +/- 2% at 350 ms, indicating that L-arginine could reduce an apamin-insensitive Ik(Ca)6. Calcium-activated potassium currents were also sensitive to charybdotoxin (10 nM), as this reduced the outward current by 34 +/- 4% at 350 ms when a high calcium-containing pipette was used during a depolarizing command to + 40 mV. L-Arginine still decreased the outward current in the presence of charybdotoxin, by 6 +/- 1% at 4.8 ms and 12 +/- 4% at 350 ms, showing that L-arginine could reduce a charybdotoxin-insensitive Ik(Ca).7. The present results indicate that NO-synthase in ciliary ganglia can modulate Ik(Ca) by a method which is independent of the action of NO on the calcium channels. The Ik(ca) is decreased significantly at 4.8 ms into a depolarizing pulse, at a time that would decrease the rate of repolarization of the action potential. Ik(Ca) is also reduced at longer times (350 ms), indicating an affect on the inactivating process.

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
D009474	Neurons	The basic cellular units of nervous tissue. Each neuron consists of a body, an axon, and dendrites. Their purpose is to receive, conduct, and transmit impulses in the NERVOUS SYSTEM.	Nerve Cells,Cell, Nerve,Cells, Nerve,Nerve Cell,Neuron
D009569	Nitric Oxide	A free radical gas produced endogenously by a variety of mammalian cells, synthesized from ARGININE by NITRIC OXIDE SYNTHASE. Nitric oxide is one of the ENDOTHELIUM-DEPENDENT RELAXING FACTORS released by the vascular endothelium and mediates VASODILATION. It also inhibits platelet aggregation, induces disaggregation of aggregated platelets, and inhibits platelet adhesion to the vascular endothelium. Nitric oxide activates cytosolic GUANYLATE CYCLASE and thus elevates intracellular levels of CYCLIC GMP.	Endogenous Nitrate Vasodilator,Mononitrogen Monoxide,Nitric Oxide, Endothelium-Derived,Nitrogen Monoxide,Endothelium-Derived Nitric Oxide,Monoxide, Mononitrogen,Monoxide, Nitrogen,Nitrate Vasodilator, Endogenous,Nitric Oxide, Endothelium Derived,Oxide, Nitric,Vasodilator, Endogenous Nitrate
D009599	Nitroprusside	A powerful vasodilator used in emergencies to lower blood pressure or to improve cardiac function. It is also an indicator for free sulfhydryl groups in proteins.	Nitroferricyanide,Sodium Nitroprusside,Cyanonitrosylferrate,Ketostix,Naniprus,Nipride,Nipruton,Nitriate,Nitropress,Nitroprussiat Fides,Nitroprusside, Disodium Salt,Nitroprusside, Disodium Salt, Dihydrate,Disodium Salt Nitroprusside,Nitroprusside, Sodium
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.
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
D002642	Chick Embryo	The developmental entity of a fertilized chicken egg (ZYGOTE). The developmental process begins about 24 h before the egg is laid at the BLASTODISC, a small whitish spot on the surface of the EGG YOLK. After 21 days of incubation, the embryo is fully developed before hatching.	Embryo, Chick,Chick Embryos,Embryos, Chick
D002923	Cilia	Populations of thin, motile processes found covering the surface of ciliates (CILIOPHORA) or the free surface of the cells making up ciliated EPITHELIUM. Each cilium arises from a basic granule in the superficial layer of CYTOPLASM. The movement of cilia propels ciliates through the liquid in which they live. The movement of cilia on a ciliated epithelium serves to propel a surface layer of mucus or fluid. (King & Stansfield, A Dictionary of Genetics, 4th ed)	Motile Cilia,Motile Cilium,Nodal Cilia,Nodal Cilium,Primary Cilia,Primary Cilium,Cilium,Cilia, Motile,Cilia, Nodal,Cilia, Primary,Cilium, Motile,Cilium, Nodal,Cilium, Primary
D005726	Ganglia, Parasympathetic	Ganglia of the parasympathetic nervous system, including the ciliary, pterygopalatine, submandibular, and otic ganglia in the cranial region and intrinsic (terminal) ganglia associated with target organs in the thorax and abdomen.	Parasympathetic Ganglia,Ciliary Ganglion,Ganglion, Parasympathetic,Otic Ganglia,Pterygopalatine Ganglia,Submandibular Ganglia,Ciliary Ganglions,Ganglia, Otic,Ganglia, Pterygopalatine,Ganglia, Submandibular,Ganglias, Otic,Ganglias, Pterygopalatine,Ganglias, Submandibular,Ganglion, Ciliary,Ganglions, Ciliary,Otic Ganglias,Parasympathetic Ganglion,Pterygopalatine Ganglias,Submandibular Ganglias
D000200	Action Potentials	Abrupt changes in the membrane potential that sweep along the CELL MEMBRANE of excitable cells in response to excitation stimuli.	Spike Potentials,Nerve Impulses,Action Potential,Impulse, Nerve,Impulses, Nerve,Nerve Impulse,Potential, Action,Potential, Spike,Potentials, Action,Potentials, Spike,Spike Potential