Static magnetic field influence on rat tail nerve function.

Motor nerve conduction and excitability were measured on the tail nerve of anesthetized rats before and after the nerve was exposed perpendicularly to a static electromagnetic field of various intensities and durations. There was no significant change in either the distal latencies or the amplitudes of the compound muscle action potential (CMAP) measured from stimulating the tail nerve after it was exposed to the electromagnetic field with a density up to 1.2 Tesla (T) for a duration of 60 seconds. However, the nerve excitability expressed as changes of the amplitudes of the submaximally evoked CMAP increased significantly when the tail nerve was exposed to a magnetic field with a density higher than 0.5T for more than 30 seconds. The finding that an electromagnetic field increases motor nerve excitability suggests a possible mechanism of its therapeutic effects.