Effect of the external concentrations of potassium and sodium on the release of (−)-[3H]noradrenaline from the adrenergic nerves of the rat vas deferens

1978 ◽  
Vol 56 (2) ◽  
pp. 323-326 ◽  
Author(s):  
A. Johns ◽  
D. M. Paton
Keyword(s):  
Action Potential ◽  
Vas Deferens ◽  
Potassium Concentration ◽  
Nerve Impulse ◽  
Sodium Concentration ◽  
Rat Vas Deferens ◽  
Adrenergic Nerves ◽  
Resting Membrane Potential ◽  
Release Of Noradrenaline ◽  
External Potassium

The effect of the external concentrations of sodium and potassium on the nerve-induced release of (−)-[3H]noradrenaline from the adrenergic nerves of the rat vas deferens has been investigated. Increasing the external potassium concentration above 5 mM decreased the amount of noradrenaline released, while reducing the external potassium concentration below 5 mM had no significant effect on the induced release of noradrenaline. Decreasing the external sodium concentration below 75 mM progressively decreased the release of noradrenaline. It is concluded that the amplitude of the action potential is optimum for release at the normal resting membrane potential, and only decreasing the amplitude of the action potential alters the amount of transmitter released per nerve impulse.

Membrane potentials in an acanthocephalan worm (Macracanthorhynchus hirudinaceus)

Parasitology ◽  
1981 ◽  
Vol 83 (1) ◽  
pp. 33-41 ◽  
Author(s):  
D. M. Miller ◽  
B. S. Wong ◽  
T. T. Dunagan
Keyword(s):  
Smooth Muscle ◽  
Membrane Potential ◽  
Calcium Ions ◽  
Potassium Concentration ◽  
Sodium Concentration ◽  
Calcium Flux ◽  
Resting Membrane Potential ◽  
Free Medium ◽  
External Potassium ◽  
Macracanthorhynchus Hirudinaceus

SUMMARYThe resting membrane potential of the acanthocephalan rete system in Macracanthorhynchus hirudinaceus was −35±1·5 mV (n = 20) and was dependent upon the external potassium concentration. The membrane potential reached 0 mV when the external potassium concentration was 160 mM. Spontaneous spike potentials of 45 mV ± 10 were dependent on calcium flux. The membrane potential was depolarized by acetylcholine, potassium-free medium, calcium ions and chloride-free medium but not by changes in the external sodium concentration. Spontaneous potentials were increased in number by acetylcholine and calcium at concentrations above 3 mM, but were decreased in number by chloride- and calcium-free medium. Hence the rete system potentials are very similar to smooth muscle potentials in many respects.

scholarly journals Relative Ion Permeabilities in the Crayfish Giant Axon Determined from Rapid External Ion Changes

1967 ◽  
Vol 50 (7) ◽  
pp. 1929-1953 ◽  
Author(s):  
Alfred Strickholm ◽  
B. Gunnar Wallin
Keyword(s):  
Membrane Potential ◽  
Potassium Level ◽  
Potassium Concentration ◽  
Giant Axon ◽  
Resting Potential ◽  
Resting Membrane Potential ◽  
Constant Field ◽  
Appreciable Effect ◽  
Ion Concentrations ◽  
External Potassium

The changes in membrane potential of isolated, single crayfish giant axons following rapid shifts in external ion concentrations have been studied. At normal resting potential the immediate change in membrane potential after a variation in external potassium concentration is quite marked compared to the effect of an equivalent chloride change. If the membrane is depolarized by a maintained potassium elevation, the immediate potential change due to a chloride variation becomes comparable to that of an equivalent potassium change. There is no appreciable effect on membrane potential when external sodium is varied, at normal or at a depolarized membrane potential. Starting from the constant field equation, expressions for the permeability ratios PCl/PK, PNa/PK, and for intracellular potassium and chloride concentrations are derived. At normal resting membrane potential, PCl/PK is 0.13 but at a membrane potential of -53 mv (external potassium level increased about five times) it is 0.85. The intracellular concentrations of potassium and chloride are estimated to be 233 and 34 mM, respectively, and it is pointed out that this is not compatible with ions distributed in a Nernst equilibrium across the membrane. It is also stressed that the information given by a plot of membrane potential vs. the logarithm of external potassium concentrations is very limited and rests upon several important assumptions.

The effects of the ionophore A-23187 on the rat vas deferens

1983 ◽  
Vol 61 (1) ◽  
pp. 97-101 ◽  
Author(s):  
M. W. Warenycia ◽  
M. M. Vohra
Keyword(s):  
Vas Deferens ◽  
Calcium Ionophore ◽  
Rat Vas Deferens ◽  
Adrenergic Nerves ◽  
Time Dependent ◽  
Dependent Manner ◽  
Concentration Dependent Manner ◽  
A 23187 ◽  
Endogenous Noradrenaline ◽  
Rhythmic Contractions

The calcium ionophore A-23187 induced spontaneous, rhythmic contractions in the rat isolated vas deferens in a concentration-dependent manner. Contractions were blocked by phentolamine and were abolished following pretreatment with reserpine. In tissues preloaded with [3H]noradrenaline, A-23187 (10 μM) caused a time-dependent increase in the release of tritium. The findings suggest that A-23187-induced contractions in the rat vas deferens are secondary to the release of endogenous noradrenaline from the adrenergic nerves, as are contractions induced in this preparation by X-537A (another calcium ionophore) described earlier by other investigators.

scholarly journals EFFECTS OF POTASSIUM, SODIUM, AND AZIDE ON THE IONIC MOVEMENTS THAT ACCOMPANY ACTIVITY IN FROG NERVES

1958 ◽  
Vol 41 (6) ◽  
pp. 1187-1203 ◽  
Author(s):  
Tomoaki Asano ◽  
W. P. Hurlbut
Keyword(s):  
Potassium Concentration ◽  
Compound Action Potential ◽  
Sodium Concentration ◽  
Sodium Content ◽  
Bathing Solution ◽  
External Potassium ◽  
Rate Of Decline ◽  
Ionic Movements ◽  
Sodium And Potassium ◽  
Compound Action

Stimulation of intact or desheathed frog sciatic nerves produced an increase in the sodium content and a decrease in the potassium content of this tissue. In desheathed preparations the magnitudes of the changes in ionic contents decreased as the concentration of the potassium in the bathing solution was increased, while changing the external sodium concentration produced small effects on the ionic shifts. During tetanization, the rate of decline of the compound action potential also decreased as the external potassium concentration increased. Eliminating the activity respiration with 0.2 mM azide did not greatly modify the changes in sodium and potassium distribution that accompanied activity in either intact or desheathed nerves.

scholarly journals EFFECTS OF EXTERNAL IONS ON MEMBRANE POTENTIALS OF A CRAYFISH GIANT AXON

1959 ◽  
Vol 42 (5) ◽  
pp. 971-982 ◽  
Author(s):  
John C. Dalton ◽  
Keyword(s):  
Action Potential ◽  
Inverse Function ◽  
Giant Axon ◽  
Sodium Concentration ◽  
Resting Potential ◽  
Transmembrane Potentials ◽  
External Potassium ◽  
Ionic Effects ◽  
External Calcium ◽  
Good Agreement

Transmembrane potentials in the crayfish giant axon have been investigated as a function of the concentration of normally occurring external cations. Results have been compared with data already available for the lobster and squid giant axons. The magnitude of the action potential was shown to be a linear function of the log of the external sodium concentration, as would be predicted for an ideal sodium electrode. The resting potential is an inverse function of the external potassium concentration, but behaves as an ideal potassium electrode only at the higher external concentrations of potassium. Decrease in external calcium results in a decrease in both resting potential and action potential; an increase in external calcium above normal has no effect on magnitude of transmembrane potentials. Magnesium can partially substitute for calcium in the maintenance of normal action potential magnitude, but appears to have very little effect on resting potential. All ionic effects studied are completely reversible. The results are in generally good agreement with data presently available for the lobster giant axon and for the squid giant axon.

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