A delayed all-or-none hyperpolarisation induced by a single Ca action potential in hamster eggs |
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Authors: | A I McNiven S Yoshida P Georgiou C R House |
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Institution: | (1) Department of Preclinical Veterinary Sciences, University of Edinburgh, Summerhall, EH9 1QH Edinburgh, UK |
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Abstract: | A transient change of membrane potential and resistance could be evoked after a long latency (ca. 9 s) by a single calcium action potential in some unfertilised hamster eggs. The estimated reversal potential for the delayed response was close to EK supporting the conclusion that K channels were opened indirectly by the Ca2+ influx through voltage-gated channels. A second action potential elicited after the first did not induce a similar response. A number of treatments (insertion of a Ca2 pipette, application of Na+-free solution, La3+ or high external pH) likely to raise Ca2+]i also induced similar large changes of potential and resistance after which a single action potential failed to evoke a large delayed response. The evidence indicates that a small rise in Ca2+]i activates a slow process leading to a further large increase in Ca2+]i. |
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Keywords: | Ca2+ release Ca2+-mediated K conductance Cocytes Hamster |
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