MGLUR ACTIVATION REVEALS A TONIC NMDA COMPONENT IN INFLAMMATORY HYPERALGESIA

METABOTROPIC glutamate receptors (mGluRs) have been shown to contribut e to nociceptive processing in the spinal cord. We have investigated t he pharmacology of the mGluR agonist (1S,3R)-ACPD during inflammatory hyperalgesia in an in vitro preparation of the juvenile rat hemisected spinal cord. Superfusion of (1S,3R)-ACPD produced a concentration-dep endent ventral root depolarization in naive and hyperalgesic animals w ith no significant difference in EC50 values (55.5 +/- 6.36 mu M and 5 1.0 +/- 5.76 mu M, respectively, n = 4). However, the amplitude of the maximum response was significantly enhanced by 23% in hyperalgesic co mpared with naive animals. The NMDA receptor antagonist D-APS reversed this effect, leaving the (1S,3R)-ACPD dose-response curve unchanged i n naive animals. These results suggest a tonic NMDA component in the s pinal cord during inflammatory hyperalgesia. (C) 1998 Rapid Science Lt d.