Modulation of the Potassium Conductance in the Squid Giant Axon

  • Eduardo Perozo
  • Christina K. Webb
  • Francisco Bezanilla


The potassium conductance of the squid giant axon is considered the classical example of the delayed rectifier-type of voltage dependent potassium permeability (Hodgkin and Huxley, 1952). In this preparation a large number of experiments have been done on K ionic currents using intact axons and under conditions of internal perfusion to study the selectivity and voltage dependence of the conductance. It has also been possible to record single channel events (Conti and Neher, 1980; Llano and Bezanilla, 1985; Llano, Webb and Bezanilla, 1987) and gating currents related to the movement of the charge responsible for the opening and closing of the K conductance (White and Bezanilla, 1985). The squid giant axon is then an ideal preparation for a detailed analysis of K channel gating because all types of electrophysiological recordings can be made in the same preparation, an important prerequisite for formulating a complete model of channel gating. We review here evidence that the K conductance in the squid axon is modulated by ATP-dependent phosphorylation. The changes induced by ATP in the macroscopic currents appear to be the result of a combined effect on more than one type of K channel. We also provide evidence for a Ca-activated component of the K conductance.


Current Amplitude Voltage Dependence Internal Solution Voltage Shift Potassium Conductance 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.


Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.


  1. Almers, W., and Armstrong, C. M., 1980, Survival of K+ permeability and gating currents in squid axons perfused with K+-free media, J. Gen. Physiol., 75:61.CrossRefGoogle Scholar
  2. Bezanilla, F., Caputo, C., Dipolo, R., and Rojas, H., 1986, Potassium conductance of squid giant axon is modulated by ATP, Proc. Nat. Acad. Sci. U.S.A., 83(8):2743.CrossRefGoogle Scholar
  3. Bezanilla, F., Vergara, J., and Taylor, R. E., 1982, Voltage clamping of excitable membranes, in: “Methods of Experimental Physics: Biophysics,” vol. 20, G. Ehrenstein and H. Lecar, eds., Academic Press Inc., London.Google Scholar
  4. Brinley, F. J., and Mullins, L.M., 1967, Sodium extrusion by internally dialyzed squid axons, J. Gen. Physiol., 50:2303.CrossRefGoogle Scholar
  5. Conti, F., and Neher, E., 1980, Single channel recordings of K+ currents in squid axons, Nature (Lond), 285:140.CrossRefGoogle Scholar
  6. Dipolo, R., Bezanilla, F., Caputo, C., and Rojas, H., 1985, Voltage dependence of the Na/Ca exchange in voltage-clamped, dialyzed squid axons, J. Gen. Physiol., 86:457.CrossRefGoogle Scholar
  7. Ewald, D. A., Williams, A., and Levitan, I. B., 1985, Modulation of single Ca2+-dependent K channel activity by protein phosphorylation, Nature, 315:503.CrossRefGoogle Scholar
  8. Findlay, I., Dunne, M. J., and Petersen, O. H., 1985, ATP-sensitive inward rectifier and voltage and Calcium-activated K channels in cultured pancreatic islet cells, J. Memb. Biol., 88:165.CrossRefGoogle Scholar
  9. Hidaka, H., Inagaki, M., Kawamoto, S., and Sasaki, Y., 1984, Isoquinolinesulfonamides, novel and potent inhibitors of cyclic nucleotide dependent protein kinase and protein kinase C, Biochemistry, 23:5036.CrossRefGoogle Scholar
  10. Hodgkin, A. L., and Huxley, A.F., 1952, A quantitative description of membrane current and its application to conduction and excitation in nerve, J. Physiol. (Lond), 117:500.Google Scholar
  11. Kakei, M., Noma, A., and Shibasaki, T., 1985, Properties of adenosinetriphosphate-regulated potassium channels in guinea-pig ventricular cells, J. Physiol., 363:441.Google Scholar
  12. Latorre, R., 1986, The large Ca-activated potassium channel, in: “Ion channel reconstitution,” C. Miller, ed., Plenum, New York.Google Scholar
  13. Llano, I., and Bezanilla, F., 1985, Two types of potassium channels in the cut-open squid giant axon, Biophys. J., 47:221a.Google Scholar
  14. Llano, I., Webb, C. K., and Bezanilla, F., 1987, Two types of unitary potassium channel currents in the squid giant axon, In preparation.Google Scholar
  15. Miller, C., Moczydlowski, E., Latorre, R., and Phillips, M., 1985, Charybdotoxin, a protein inhibitor of single Ca2+-activated K+ channels from mammalian skeletal muscle, Nature, 313:316.Google Scholar
  16. Perozo, E., and Bezanilla, F., 1987a, Intracellular calcium modulates the potassium conductance in dialyzed squid axons, Biophys. J., 51:547a.CrossRefGoogle Scholar
  17. Perozo, E., and Bezanilla, F., 1987b, The modulation of K channels in dialyzed squid axons: Effect of intracellular calcium, In preparation.Google Scholar
  18. Perozo, E., Bezanilla, F., Caputo, C., and Dipolo, R., 1987, The modulation of K channels in dialyzed squid axons: ATP mediated phosphorylation, In preparation.Google Scholar
  19. Perozo, E., Dipolo, R., Caputo, C., Rojas, H., and Bezanilla, F., 1986, ATP modification of K currents in dialyzed squid axons, Biophys. J., 49: 215a.Google Scholar
  20. Sherry, S., Goreka, A., Kosoy, M., Debrouska, R., and Hartshore, D., 1978, Roles of calcium and phosphorylation in the regulation of the activity of Gizzard myosin, Biochemistry 17:4411.CrossRefGoogle Scholar
  21. Webb, C. K., and Bezanilla, F., 1986, K currents in perfused axons are modified by ATP, Biophys. J., 49:215a.Google Scholar
  22. Webb, C. K., and Bezanilla, F., 1987, Potassium gating currents in the perfused axon are modified by ATP, Biophys. J., 51:547a.CrossRefGoogle Scholar
  23. White, M. M., and Bezanilla, F., 1985, Activation of squid axon K channels: Ionic and gating current studies, J. Gen. Physiol., 85:539.CrossRefGoogle Scholar

Copyright information

© Plenum Press, New York 1988

Authors and Affiliations

  • Eduardo Perozo
    • 2
    • 3
    • 1
  • Christina K. Webb
    • 2
    • 1
  • Francisco Bezanilla
    • 2
    • 1
  1. 1.Marine Biological LaboratoryWoods HoleUSA
  2. 2.Department of Physiology, Ahmanson Laboratory of Neurobiology and Jerry Lewis Neuromuscular Research CenterUniversity of CaliforniaLos AngelesUSA
  3. 3.Instituto Venezolano de Investigaciones CientificasCaracasVenezuela

Personalised recommendations