Directed and enhanced neurite growth with pulsed magnetic field stimulation

Pulsed magnetic field (PMF) stimulation was applied to mammalian neurons in vitro to influence axonal growth and to determine whether induced current would direct and enhance neurite growth in the direction of the current. Tw o coils were constructed from individual sheets of copper folded into a squ are coil. Each coil was placed in a separate water-jacketed incubator. One was energized by a waveform generator driving a power amplifier, the other was not energized. Whole dorsal root ganglia (DRG) explant cultures from 15 -day Sprague-Dawley rat embryos were established in supplemented media plus nerve growth factor (NGF) at concentrations of 0-100 ng/mL on a collagen-l aminin substrate. Dishes were placed at the center of the top and bottom of both coils, so that the DRG were adjacent to the current flowing in the co il. After an initial 12 h allowing DRG attachment to the substrate floor, o ne coil was energized for 18 h, followed by a postexposure period of 18 h. Total incubation time was 48 h for all DRG cultures. At termination, DRG we re histochemically stained for visualization and quantitative analysis of n eurite outgrowth. Direction and length of neurite outgrowth were recorded w ith respect to direction of the current. PMF exposed DRG exhibited asymmetr ical growth parallel to the current direction with concomitant enhancement of neurite length. DRG cultures not PMF exposed had a characteristic radial pattern of neurite outgrowth. These results suggest that PMF may offer a n oninvasive mechanism to direct and promote nerve regeneration. (C) 2000 Wil ey-Liss, Inc.