"Action potentials" in Neurospora crassa, a mycelial fungus.

Occasional spontaneous "action potentials" are found in mature hyphae of the fungus Neurospora crassa. They can arise either from low-level sinusoidal oscillations of the membrane potential or from a linear slow depolarization which accelerates into a rapid upstroke at a voltage 5-20 mV depolarized from the normal resting potential (near-180 mV). The "action potentials" are long-lasting, 1-2 min and at the peak reach a membrane potential near-40 mV. A 2-to 8-fold increase of membrane conductance accompanies the main depolarization, but a slight decrease of membrane conductance occurs during the slow depolarization. Two plausible mechanisms for the phenomenon are (a) periodic increases of membrane permeability to inorganic ions, particularly H+ or Cl- and (b) periodic decreases in activity of the major electrogenic pump (H+) or the Neurospora membrane, coupled with a nonlinear (inverse signoid) current-boltage relationship. Identification of action potential-like disturbances in fungi means that such behavior has now been found in all major biologic taxa which have been probed with suitable electrodes. As yet there is no obvious function for the events in fungi.

[1]  N. Bagni,et al.  Magnesium and polyamine levels in Neurospora crassa mycelia. , 1971, Biochimica et biophysica acta.

[2]  R. Eckert,et al.  Bioelectric control of ciliary activity. , 1972, Science.

[3]  Balth van der Pol Jun Docts. Sc.,et al.  LXXII. The heartbeat considered as a relaxation oscillation, and an electrical model of the heart , 1928 .

[4]  C. Slayman,et al.  POTASSIUM TRANSPORT IN NEUROSPORA. I. INTRACELLULAR SODIUM AND POTASSIUM CONCENTRATIONS, AND CATION REQUIREMENTS FOR GROWTH. , 1964, Biochimica et biophysica acta.

[5]  C. Slayman,et al.  Net Uptake of Potassium in Neurospora Exchange for sodium and hydrogen ions , 1968, The Journal of general physiology.

[6]  Balth. van der Pol Jun. LXXXVIII. On “relaxation-oscillations” , 1926 .

[7]  C. Slayman,et al.  Electrogenic proton transport in the plasma membrane of Neurospora. , 1975, Biophysical Journal.

[8]  C. Slayman Electrical Properties of Neurospora crassa Respiration and the intracellular potential , 1965 .

[9]  F. Harold DEPLETION AND REPLENISHMENT OF THE INORGANIC POLYPHOSPHATE POOL IN NEUROSPORA CRASSA , 1962, Journal of bacteriology.

[10]  U. Kishimoto Voltage clamp and internal perfusion studies on Nitella internodes , 1965 .

[11]  T. Sibaoka Excitable Cells in Mimosa , 1962, Science.

[12]  C. Slayman Electrical properties of Neurospora crassa. Effects of external cations on the intracellular potential. , 1965 .

[13]  A. Lambowitz,et al.  Cyanide-Resistant Respiration in Neurospora crassa , 1971, Journal of Bacteriology.

[14]  A. Finkelstein,et al.  Electrical Excitability of Isolated Frog Skin and Toad Bladder , 1964, The Journal of general physiology.

[15]  E. B. Darden,et al.  The action potentials obtained from venus's-flytrap. , 1950, Science.

[16]  R. H. Adrian,et al.  The potassium and chloride conductance of frog muscle membrane , 1962, The Journal of physiology.

[17]  D. Noble,et al.  The kinetics and rectifier properties of the slow potassium current in cardiac Purkinje fibres , 1968, The Journal of physiology.

[18]  J. Jack,et al.  Electric current flow in excitable cells , 1975 .

[19]  G. Findlay Membrane Electrical Behaviour in Nitellopsis Obtusa , 1970 .

[20]  W. Chandler,et al.  Slow changes in membrane permeability and long‐lasting action potentials in axons perfused with fluoride solutions , 1970, The Journal of physiology.

[21]  A. Hodgkin,et al.  The dual effect of membrane potential on sodium conductance in the giant axon of Loligo , 1952, The Journal of physiology.