Exposure to a hypogeomagnetic field or to oscillating magnetic fields similarly reduce stress-induced analgesia in C57 male mice

Previous studies have shown that exposure to altered magnetic fields alters analgesic responses in a variety of species, including humans. Here we examined whether deprivation of the normally occurring geomagnetic field also affects stress-induced analgesia, by measuring the nociceptive responses of C57 male mice that were restraint-stressed in a hypogeomagnetic environment (inside a mu-metal box). Stress-induced analgesia was significantly suppressed in a manner comparable to that observed in mice that were either exposed to altered oscillating magnetic fields or treated with the prototypic opiate antagonist naloxone. These results represent the first piece of evidence that a period in a hypogeomagnetic environment inhibits stress- induced analgesia.