Alternating current threshold excitation of space-clamped squid giant axons was measured as a function of frequency, external calcium concentration, temperature (from 10° to 35°C), and hyper- and depolarizing steps. In normal axons there is usually an optimum frequency at about 120 Hz, at which the threshold is a minimum. The threshold rises at both lower and higher frequencies to give a resonance curve. Low calcium causes an increase in optimum frequency, a decrease in current threshold, and an increase in sharpness of tuning in both real axons and axons computed according to the Hodgkin-Huxley formulation; high calcium causes opposite effects. An increase in temperature causes an increase of optimum frequency, an increase in sharpness of tuning, and an increase in threshold current in both real and computed axons. The Q10 for the effect of temperature upon optimum frequency is 1.8 in real and computed axons at moderate temperatures. Hyperpolarization causes (a) a decrease in optimum frequency, (b) a decrease in sharpness of tuning, and (c) an increase in threshold. Depolarization causes opposite effects.
Article|
September 01 1971
Effect of Calcium, Temperature, and Polarizing Currents upon Alternating Current Excitation of Space-Clamped Squid Axons
Rita Guttman,
Rita Guttman
From the Department of Biology, Brooklyn College, Brooklyn, New York 11210, and Marine Biological Laboratory, Woods Hole, Massachusetts 02543.
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Lon Hachmeister
Lon Hachmeister
From the Department of Biology, Brooklyn College, Brooklyn, New York 11210, and Marine Biological Laboratory, Woods Hole, Massachusetts 02543.
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Rita Guttman
From the Department of Biology, Brooklyn College, Brooklyn, New York 11210, and Marine Biological Laboratory, Woods Hole, Massachusetts 02543.
Lon Hachmeister
From the Department of Biology, Brooklyn College, Brooklyn, New York 11210, and Marine Biological Laboratory, Woods Hole, Massachusetts 02543.
Mr. Hachmeister's present address is Department of Oceanography, University of Washington, Seattle, Washington 98115.
Received:
March 09 1971
Online Issn: 1540-7748
Print Issn: 0022-1295
Copyright © 1971 by The Rockefeller University Press
1971
J Gen Physiol (1971) 58 (3): 304–321.
Article history
Received:
March 09 1971
Citation
Rita Guttman, Lon Hachmeister; Effect of Calcium, Temperature, and Polarizing Currents upon Alternating Current Excitation of Space-Clamped Squid Axons . J Gen Physiol 1 September 1971; 58 (3): 304–321. doi: https://doi.org/10.1085/jgp.58.3.304
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