Voltage and pharmacological modification of membrane currents during the action potential in Chara inflata

Kourie, J.I.

Desalination 106(1-3): 435-438


ISSN/ISBN: 0011-9164
DOI: 10.1016/s0011-9164(96)00143-9
Accession: 017657093

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The transient inward, Ii(max) and the delayed outward I(max)., currents in C. inflata were triggered in an all-or-none fashion. At a test potential of 60 mV a clamping duration of 100 ms to 250 ms was sufficient to trigger the transient inward current and stop the cytoplasmic streaming. The reversal potentials deduced from the current-voltage relations of the components indicate that the transient inward, Ii(max), was carried by Cl and the delayed outward, I(max), by K+. The negative prepulse enabled reproducibility of Ii(max) and I(max). TEA+ (tetraethylammonium) induced action potentials in C. inflata and hyperpolarized the free running membrane potential, Vm, in C. corallina. In voltage-clamp experiments, TEA+ blocked Ii(max), and increased Ii(max). In the hyperpolarized state, 1 mM 9-AC (9-anthracenecarboxylic acid), a Cl channel blocker, prevented the NaCl-induced depolarization in Vm, hyperpolarized the Vm by 20 to 40 mV and increased the membrane resistance.