Evidence for the involvement of glutamatergic receptors in the antinociception caused in mice by the sesquiterpene drimanial.

Drimanial, a new sesquiterpene isolated from the barks of the plant Drimys winteri (Winteraceae), given systemically, intraplantarly, or by spinal or supraspinal routes, produced pronounced antinociception against both phases of formalin-induced licking. The systemic injection of drimanial also inhibited, in a graded manner, the pain-related behaviours induced by intraplantar or intrathecal (i.t.) administration of glutamate. Moreover, drimanial also caused marked inhibition of the nociception induced by i.t. administration of a metabotropic glutamate agonist (1S,3R)-ACPD, without affecting nociceptive responses induced by ionotropic agonists (NMDA, kainate, AMPA) or by substance P. The antinociception caused by drimanial was not influenced by naloxone, nor did it interfere with the motor coordination of animals in the rota-rod test. Furthermore, drimanial caused graded inhibition of [(3)H]glutamate binding in cerebral cortical membranes from mice, with an IC(50) value of 4.39 micro M. Together, these results provide strong evidence indicating that the sesquiterpene drimanial produces antinociception in mice at peripheral, spinal and supraspinal sites. An interaction with metabotropic glutamate receptors seems to contribute to the mechanisms underlying its antinociceptive action.