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EFFECTS OF STEADY MAGNETIC FIELDS ON ACTION POTENTIALS OF SENSORY NEURONS IN VITRO
Michael J. McLean, M.D., Ph.D., Robert R. Holcomb, M.D., Ph.D., Artur W. Wamil, M.D., Ph.D., Joel D. Pickett, M.D.
ABSTRACT
Exposure to a static field (10 milliTesla) produced
by an array of four permanent magnets of alternating polarity (side, facing
neuron under study) reduced or blocked action potential (AP) firing by
adult mouse dorsal root ganglion neurons in monolayer disassociated cell
culture.
The effect was reversible with slow recovery of firing over several minutes.
Arrays of four magnets of like polarity (all positive or all negative
poles; 32-35 milliTesla) also reduced firing, but APs returned within
seconds after removal of these arrays. An alternating dipolar array (13.7
milliTesla) had no effect. These findings suggest that the configuration
of magnets and gradients within the field may be more important than field
strength in determining biological effects.
Devices controlling such magnetic fields could be used for the treatment
of chronic, medication-resistant pain. static magnetic fields, magnetic
field gradient, action potentials (AP), cell culture, dorsal root ganglion
cells.
INTRODUCTION
At this time of heightened public concern about the health impact of magnetic fields, there is increasing use of magnetic devices in the practice of clinical medicine. Examples include magnetic resonance imaging of body structures; the use of SQUID (semiconductive quantum interference device) probes to detect magnetic fields produced by cardiac and neural tissue; the use of pulsed magnetic fields to enhance bone healing8; and, the historical use of magnets to treat pain.
Yet, understanding of cellular effects of magnetic fields is in its infancy. Theoretical studies have indicated that homogeneous fields of 25-100 Tesla (T: SI unit of magnetic field density) would be required to affect ionic currents of nerve processes.10,11 Studies of effects of homogeneous fields (up to 10 T) on non-mammalian preparations have yielded mixed results. Some studies reported effects on aspects of neuronal excitability, such as chronaxie, action potential firing and/or response to neurotransmitters.
Extensive laboratory testing has shown that it's not the magnetic field strength, but the field gradient (steepness of the slope of the magnetic field) that is the determining factor in alleviating pain. This unique steep field gradient generated by the Quadrapolar array is what blocks the pain signal.
This is why the QuadraBloc™ Science is so effective when placed over the irritated nerve.
Over a decade of cell research was done at Vanderbilt University Medical Center in Nashville Tennessee and clinical data was collected at various Medical Centers and Universities around the world.
