MAGNESIUM-DEFICIENCY INDUCES AN HYPERALGESIA REVERSED BY THE NMDA RECEPTOR ANTAGONIST MK801

The aim of this study was to determine the changes of the nociceptive thresholds in response to an acute mechanical stimulus (paw pressure) in magnesium (Mg)-deficient rats, and the involvement of the NMDA rece ptor in these changes. Changes in vocalization thresholds was determin ed after 7 days of feeding with a Mg-depleted diet. Compared with the control group, Mg-deficient rats showed a significant decrease in the vocalization thresholds (-35.8 +/- 2.5%, p < 0.001) reflecting hyperal gesia. In Mg-deprived rats, three doses (0.06, 0.12 and 0.24 mg/kg s.c .) of dizocilpine (MK801), a non-competitive NMDA receptor antagonist, significantly reversed the hyperalgesia in a dose-dependent manner fo r at least 48 h. No effect of MR801 was observed in the control group. These data provide evidence that Mg deficiency could constitute a new model of hyperalgesia involving NMDA receptors.