Alteration of the conductance of Na+ channels in the nodal membrane of frog nerve by holding potential and tetrodotoxin |
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Authors: | B Neumcke R Stämpfli |
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Institution: | I. Physiologisches Institut, Universität des Saarlandes, D-6650 Homburg/Saar F.R.G. |
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Abstract: | (1) Na+ currents and Na+-current fluctuations were measured in myelinated frog nerve fibres at 15°C during 7.7 ms depolarizations to . (2) The conductance γ of a single Na+ channel and the number of channels per node were calculated from ensemble average values of the mean Na+ current and the variance of Na+-current fluctuations. (3) For a hyperpolarizing holding potential of the mean values of the channel conductance and number were and . (4) After changing the holding potential to the resting potential () the conductance γ increased by a factor of 1.37 whereas the number decreased by a factor of 0.60. (5) Addition of 8 nM tetrodotoxin at a holding potential of increased γ by a factor of 1.55 and reduced by a factor of 0.25. (6) The increase of the channel conductance at reduced channel numbers suggests negative cooperativity between Na+ channels in the nodal membrane. |
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Keywords: | Fluctuation analysis Tetrodotoxin Channel-channel interaction Nerve membrane |
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