The Effects of Moderate-Intensity Inhomogeneous Static Magnetic Fields on Neuromuscular Transmission

The present study focuses on the effects of moderate-intensity inhomogeneous static magnetic fields (SMF) up to 0.73 T on action potentials in Wistar rats. Thirty three animals were divided into three groups: a sham-exposed control group and two exposed groups with exposure to maximum flux densities (Bmax) of 0.24 and 0.73 T SMF. The amplitude of the electrically evoked compound nerve action potentials (CNAP) and compound muscle action potentials (CMAP) were measured for up to 2 h. In the CNAP, the excitation of Aδ fibers was significantly enhanced by both 0.24 T and 0.73 T SMF for 2 h, relative to the sham-exposed control. Furthermore, the CMAP decrement was significantly enhanced by 0.73 T SMF for 1 to 2 h, but not by 0.24 T SMF for up to 2 h, compared with the control. These results suggest that SMF (0.24 and 0.73 T for 2 h) enhances pain perception because the Aδ fibers are responsible for pain transmission. In addition, SMF (0.73 T for 1 to 2 h) may modulate neuromuscular transmission. Thus, the magnetic force produced by SMF could affect the behavior of some types of ion channels associated with Aδ fibers, probably due to SMF-induced modulation of ion/ligand binding and ion transport.