Abstract
Magnetic applications have been used to treat painful stimuli in various contexts. Magnetic fields that mimic electrophysiological patterns have been referred to as complex magnetic fields. In 7 different experiments, the optimal parameters for producing a robust analgesia (equivalent to about 4 mg/kg of morphine) in male rats to thermal stimuli following exposures to weak (1 microTesla (μT)) complex magnetic fields were explored. Thermal nociceptive thresholds for male Wistar rats were examined after exposure to the experimental treatment. Two different complex magnetic patterns were investigated for their potential analgesic effects. Rats were exposed (whole body) to a magnetic field treatment for a pre-defined duration usually lasting 30 min unless otherwise specified. The parameters evaluated for eliciting analgesia included the optimal time delay between successive presentations of the magnetic field, total length of magnetic field exposure, and the duration the specific values that generated the total pattern were activated. Maximum analgesia occurred when patterns of magnetic fields with burst-firing-like configurations lasting 690 msec were presented once every approximately 4 sec for 30 min rather than 60 min. Rats with histories of epilepsy and brain damage showed maintained elevation of nociceptive thresholds for at least one week after a single exposure to these magnetic fields. A different frequency-modulated pattern also produced an analgesic response that lasted for 4 h following an exposure of 30 min but not 2 h. A constantly generated pattern derived from a chaos (May algorithm) function produced similar levels of analgesia. The results of these experiments suggest that rational designs of the temporal structures of weak magnetic fields may be a novel, inexpensive, and, reliable technique for producing analgesia to some classes of painful stimuli.