Publications and Research

Document Type

Article

Publication Date

September 1971

Abstract

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.

Share

COinS
 
 

To view the content in your browser, please download Adobe Reader or, alternately,
you may Download the file to your hard drive.

NOTE: The latest versions of Adobe Reader do not support viewing PDF files within Firefox on Mac OS and if you are using a modern (Intel) Mac, there is no official plugin for viewing PDF files within the browser window.