COMPARISON OF NOCICEPTIVE EFFECTS PRODUCED BY INTRATHECAL ADMINISTRATION OF MGLUR AGONISTS

THE present study examined the mGluR subtypes involved in (1S,3R)-ACPD -induced spontaneous nociceptive behaviours (SNB) by administering the following selective agonists by the intrathecal (i.t.) route: (RS)DHP G, trans-ADA (Group I; mGluR1/5 and mGluR5, respectively), (1S,3S)-ACP D, (2R,4R)-APDC (Group II), and L-AP4 (Group III). (RS)-DHPG administr ation induced SNB that were of significantly greater intensity and lon ger duration than those induced by an equal dose of (1S,3R)-ACPD. No o ther agonists produced SNB, except (1S,3S)-ACPD, which may be attribut able to a nonselective action at mGluR1. Intrathecal treatment with th e mGluR antagonist (+)-MCPG or the NMDA antagonist D-AP5 prior to (RS) -DHPG administration dose-dependently reduced SNB. It is suggested tha t a possible interaction between NMDA and mGluR1 is a critical event i n the maintenance of persistent nociception.