Axonal and glial currents activated during the post-tetanic hyperpolarization in non-myelinated nerve.
Pflugers Arch
; 436(4): 529-37, 1998 Jul.
Article
in En
| MEDLINE
| ID: mdl-9683725
ABSTRACT
Changes in membrane potential and potassium concentration in the extracellular space ([K+]e) of rabbit vagus nerve were measured simultaneously during electrical activity and during the period of recovery using a modified sucrose-gap method and potassium-sensitive microelectrodes. After stimulation for 15 s at 15 Hz the main activity-induced increase in [K+]e reached 16.9 mM. This increase in [K+]e was paralleled by a depolarization of the preparation. The period of activity was followed by a post-tetanic hyperpolarization (PTH) lasting tens of seconds, generated by the axonal electrogenic Na+-K+ pump and to a lesser extent by the pump of the surrounding Schwann cells. The amplitude of the PTH dramatically increased in experiments in which inward currents were blocked by removal of Cl or after application of Cs+ or Ba2+, indicating that under normal conditions the current generated by the Na+-K+ pump is strongly short-circuited. A pharmacological and kinetic study showed that these currents are (1) the hyperpolarization-activated current I h, and (2) the inwardly rectifying I KIR current. The results show that the latter originates from Schwann cells. Our data indicate that in non-myelinated nerves there is a subtle association of inward ionic channels which (1) helps the cell to maintain an optimal membrane potential after a period of activity, and (2) contributes to the removal of excess K+ from the extracellular space.
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Collection:
01-internacional
Database:
MEDLINE
Main subject:
Axons
/
Neuroglia
/
Membrane Potentials
Limits:
Animals
Language:
En
Journal:
Pflugers Arch
Year:
1998
Document type:
Article
Affiliation country:
Switzerland