Investigation of pulsed electromagnetic fields effects on potassium channels in regenerated rat sciatic nerves by sucrose-gap recording technique

ABSTRACT Investigation of pulsed electromagnetic fields effects on potassium channels in regenerated rat sciatic nerves by sucrose-gap recording technique In the peripheral nerve system, remyelination is more important for full restoration of nerve conduction functions following a nerve crush. Investigations have demonstrated that pulsed electromagnetic field (PEMF) can promote regeneration, but the mechanisms of PEMF that stimulates nerve regeneration unresolved. Therefore, the main objective of this work was to determinate whether electrophysiological changes occurring in the regenerating sciatic nerves after injury under the PEMF. We used sucrose-gap technique to demonstrate the contributions of ion channels in the electrophysiological functions of the rat sciatic nerves after crush injury. 4-Aminopyridine (Ap) and Tetraethylammonium were used to assess K* channel sensitivity during after remyelination. In addition, we made the measurements of conduction velocity of nerves and the structural changes in the nerves investigated with electron microscope. The results showed that the influence of PEMF on nerve regeneration was appeared after 38 days following the injury. PEMF particularly changed the actions of 4-Ap. Namely, amplitude of the delayed depolarization dropped, its duration prolonged and activity of the hyperpolarizing afterpotential decreased. Furthermore, PEMF caused an increase in the conduction velocity. These results suggest that full axonal myelination more critical for the electrical properties of the nerves. Even minimal damage at myelinated regions can cause significant functions of the ion channels. There are several differences in architecture and electrophysiological properties of regenerating nerve fibers, as compared with the nerves before injury. When PEMF apply to the rat with injured nerve for a long period, the myelination process may be accelerated by PEMF. Key Words: Pulsed electromagnetic field, Nerve regeneration, Nerve crush injury, Compound action potential, Rat Sciatic nerve. XVI