The Voltage Clamp

Alan J. McComas

in Galvani’s Spark

Published in print August 2011 | ISBN: 9780199751754
Published online September 2011 | e-ISBN: 9780199897094 | DOI:
The Voltage Clamp

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Now in Chicago, Kenneth Cole employs a negative feedback circuit, devised by a colleague, to clamp the voltage across the membrane of the squid giant axon. He shows that during the action potential there is an initial inward current followed by an outward current, and he attributes the latter to potassium ions. Hodgkin visits Cole who shows him the new technique and loans him some of the apparatus needed for voltage-clamp work. Within a few months Hodgkin has his own voltage-clamp system built and resumes work with Huxley on the squid giant axon at Plymouth, initially with Katz as well. By replacing sodium in the bathing fluid with choline, they are able to show that the early inward current during the action potential is indeed a sodium one, and that the later, outward, current is carried by potassium ions. On the basis of the experimental data Huxley is able to derive an equation describing the flow of current through the nerve membrane at any instant. He and Hodgkin introduce special terms which they interpret as the effects of mobile particles within the membrane. From their equations, Huxley is able to compute the form and conduction velocity of the action potential. The British voltage-clamp work is published in five papers and creates a stir; however, Cole’s assistance is not acknowledged. Hodgkin and Huxley share the 1963 Nobel Prize with Eccles.

Keywords: Kenneth Cole; Alan Hodgkin; Andrew Huxley; voltage-clamp; sodium current; potassium current; squid axon; Hodgkin-Huxley equations

Chapter.  4502 words.  Illustrated.

Subjects: Neuroscience

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