Plateau potential: Supplemental material

Supplementary information for the "Plateau potential" entry in the 2003 Web-CDROM edition of the Encyclopedia of Neuroscience, edited by George Adelman and Barry Smith (Elsevier, publ.), maintaind by Dan Hartline. Additions, corrections and suggestions are welcome
UNDER CONSTRUCTION
Last update: 4/13/05

INDEX

  1. Updates
  2. Historical
  3. Distribution of plateaus
  4. Criteria for plateaus
  5. Roles / properties of plateaus
  6. Non-neuronal plateaus
  7. Literature
  8. Citations

1. Updates, Feedback and Further Details

2. Historical

The original term "plateau potential" derived from the plateau phase in the action potential of the vertebrate heart (Wiedmann 1951). Using microelectrodes recently introduced into the electrophysiological literature by Ling and Gerard (1949), Weidmann recorded cardiac action potentials from sheep Purkinje fibers. Using a second microelectrode in the same fiber to pass current, he was able to demonstrate the all-or-nothing nature not only of the initiation of the cardiac action potential, but of its repolarization during its plateau phase. This is now recognized as a diagnostic “signature” of a plateau mechanism, derived from the “N”-shaped I(V) relation for the plateau-sustaining membrane.

3. Distribution (neural)

(For further information, click on the links)

Vertebrates

Invertebrates

4. Criteria for plateaus

The original defining criterion for a plateau, prolonged membrane bistability, was established by Weidmann (1951). Several additional physiological tests for plateaus were listed by Russell and Hartline (1982) based on their studies in lobster stomatogastric ganglion (see also Hartline and Graubard 1992 for more details). The criteria are not absolute, and not all may be present in a plateauing cell at one time or under a given set of conditions. Generally in the following list, the more critical criteria are listed first, followed by "softer" ones:
  1. Trigger test: Prolonged depolarizations (spike bursts in spiking cells) can be triggered by brief depolarizing inputs.
  2. Termination test: The depolarized (plateau) state can be terminated abruptly by brief hyperpolariging inputs.
  3. Threshold test: Triggering and termination are threshold phenomena.
  4. "All-or-nothing" test: Responses to both triggering and terminating stimuli are independent of the magnitude of the applied stimulus.
  5. Regenerative test: Responses grow after the end of a stimulus in either depolarizing or hyperpolarizing direction.
  6. Refractoriness test: following all-or-nothing termination of a depolarized state, it is more difficult to trigger a second plateau (typical but not essential).
  7. Symmetrical pulse test: Comparing responses to depolarizing and hyperpolarizing pulses, the membrane response is greater in the direction of the transition (depolarizing from a rest state; hyperpolarizing from a plateau state).
  8. Accelerating trajectory test:Characteristic accelerating membrane potential trajectories, in both depolarizing and hyperpolarizing directions in response to injected current.
  9. Membrane potential excursion test: Larger membrane potential excursions occur than can be accounted for on the basis of observed synaptic inputs.
  10. Critical hyperpolarization test: Membrane potential oscillation amplitude is suppressed in an all-or-nothing manner at some point as hyperpolarizing current offset is increased. The "all-or-nothing" character may occur as "missed" bursts in an ongoing pattern (EPSPs typically grow in magnitude with hyperpolarization owing to reversal potential effects).
  11. "Discontinuous" V(I) test: Isochronal V(I)) curves (voltage response at a fixed time folllowing onset of an injected current) show abrupt transitions from more hyperpolarized to more depolarized states or the reverse as injected current is slowly changed.
  12. Graded burst-rate test: Overall burst rates or periods of depolarization in an ongoing network pattern are modulated by sustained injection of current. Bursts of spikes are less frequent as the cell is artificially hyperpolarized. If the cell is being driven by a network, this is manifest by the "skipping" of burst activity cycles rather than the smooth gradation in burst rates seen in pacemaker bursters.
  13. Endogenous burst test: If rhythmic synaptric driving is eliminated, endogenous repetitive bursting may result if restorative and "pacemaker" mechanisms are present; note that other mechanisms for endogenous repetitive bursting are also found in neurons.

5. Ionic mechanisms

Plateaus described to date derive from voltage-dependent inward current mechanisms that produce an "N"-shaped I(V) relation in the membrane. The negative slope region of this relation (regenerative characteristic) results in two points of stable membrane potential, one near rest and the other in a depolarized "plateau" state. Two mechanisms, calcium and persistent sodium, are the primary ones involved.

6. Roles/Properties of plateaus

Plateaus promote a variety of characteristics in cells possessing them.
  1. Burst formation
  2. Quasistable switch-like properties: either "on" or "off"
  3. Temporal contrast: abriupt transitions between silence and high-frequency firing
  4. Increased "gain" for synaptic input: weak inputs can control (initiate or terminate) strong output
  5. Source of strong depolarization, hence high-frequency firing.
  6. "Trigger" mode operation: Output consequences outlast the brief inputs that trigger them
  7. Opportunities for regulatory control via modulatory input
  8. Wind up in firing freuqency

7. Non-neuronal plateaus

Plateaus are found in a variety of non-neural cell types:

8. Literature

9. Citations for this page

  • Clay JR On the persistent sodium current in squid giant axons (2003) J Neurophysiol89: 640-644 http://jn.physiology.org/cgi/content/abstract/89/1/640?etoc
  • Hartline, D. K. and Graubard, K. (1992) "Cellular and synaptic properties in the crustacean stomatogastric nervous system" in Harris-Warrick, R.M., Marder, E., Selverston, A.I. and Moulins, M. (eds) Dynamic Biological Networks: The Stomatogastric Nervous System MIT PRess: Cambridge, MA pp 31-85.
  • Ling G., and Gerard, R.W. (1949) J. cell. Comp. Physiol. 34: 383 –
  • Powers RK, and Binder MD (2003) Persistent sodium and calcium currents in rat hypoglossal motoneurons J Neurophysiol 89: 615-624 abstract
  • Ramirez, J-M and Pearson, K.G. (1993) "Alteration of bursting properties in interneurons during locust flight" J. Neurophysiol. 70: 2148-
  • Rudberg P. and Sand, O. (2000) "Bistable membrane potential of the ciliate Coleps hirtus". J exp Biol. 203: 757-64.
  • Russell, D.F. and Hartline, D.K. (1982) "Slow active potentials and bursting motor patterns in pyloric network of the lobster Panulirus interruptus J. Neurophysiol. 48: 914-937 [PDF]
  • Weidmann, S. (1951): Effect of current flow on the membrane potential of cardiac muscle. J Physiol Lond 115: 227-236

    10. Recent literature

  • Hornby TG, Rymer WZ, Benz EN, and Schmit BD (2003) Windup of flexion reflexes in chronic human spinal cord Injury: A marker for neuronal plateau potentials? J Neurophysiol 89: 416-426 abstract

    Links to related sites

    Hartline Home Page. Stomatogastric Nervous System web site Pacemaker potential page.