Effects of Na+ channel inactivation kinetics on metabolic energy costs of action potentials

  • Authors:

  • Patrick Crotty;William B. Levy

  • Affiliations:

  • Department of Neurosurgery, University of Virginia Health System, P.O. Box 800420, Charlottesville, VA, 22098-0420, USA;Department of Neurosurgery, University of Virginia Health System, P.O. Box 800420, Charlottesville, VA, 22098-0420, USA

  • Venue:
  • Neurocomputing
  • Year:
  • 2007

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Abstract

We investigate whether the inactivation properties of Na^+ channels in squid giant axons show evidence of having been optimized by evolution so as to reduce the energy expenditure associated with propagating action potentials. Using Hodgkin-Huxley-type models of the squid giant axon and varying the voltage dependence and overall scaling of the Na^+ inactivation rate, we find that faster inactivation rates correspond to less costly and more energy-efficient action potentials. However, and in contrast to the case when the ionic conductances and axon diameters are varied, the metabolic energy consumption does not have a minimum when restricted to an isovelocity curve in the phase space associated with these inactivation parameters. This failure-to-optimize encourages other hypotheses about the evolution and functionality of inactivation, such as its effects on information rates.