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pubmed:abstractText |
The influence of several ions on the membrane potential of the somatic muscle of Ascaris has been investigated by changing their concentration in the surrounding solution. When [K](o) is increased at the expense of [Na](o) leaving [Cl](o) constant, the membrane potential is first seen to increase. [K](o) higher than 45 mM reduces the membrane potential with a slope of 23 mv for a tenfold change in [K](o). However, when [K](o) is increased keeping [Na](o) and [Cl](o) low and constant, the line relating the membrane potential with log [K](o) has a slope of almost 50 mv. If [Cl](o) is reduced in the absence of external Na, after the [K](o) is increased to 45 mM, the membrane potential decreases with a slope of 59 mv per tenfold change in [Cl](o) in close agreement with the Nernst equation. If Cl(-) is replaced by SO(4) (2-), a depolarization is produced, while chloride replacement by NO(3) (-), Br(-), and I(-) results in a hyperpolarization of the membrane. Removal of the external Na(+) ions increases the average membrane potential by 17 mv.
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