| Abstrakt: |
The membrane potential in guinea-pig's papillary muscles was recorded either by a sucrose-gap method or by an intracellular microelectrode. External application of tetraethylammonium ion (TEA) in a concentration of 20 mM did not induce any appreciable effect on the action potential. However, when TEA was applied to the inside of muscle fibers by diffusion from the cut end in the potential pool, action potentials elicited in normal Tyrode's after the healing-over were prolonged. The duration of the action potential at 90% repolarization increased by a factor of up to 1.6. The dose-response relationship suggests the formation of a complex between TEA and a receptor with a dissociation constant of 2 mM. Similar prolongations developped gradually when TEA was made to diffuse from the cut end in the current pool filled with 142 mM-TEA. In conclusion, TEA caused the prolongation of the action potential acting from the inside of the membrane in guinea-pig's myocardium. The prolongation induced by TEA suggests that outward potassium current accelerates the repolarization in the normal cardiac muscle. [ABSTRACT FROM AUTHOR] |
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