Evidence for the involvement of glutamatergic and neurokinin 1 receptors in the antinociception elicited by tramadol in mice.

This study was designed to evaluate the role of spinal glutamatergic receptors and neurokinin 1-mediated pathway in the antinociception elicited by tramadol in mice. Tramadol (1-50 mg/kg), given intraperitoneally (i.p.), produced significant inhibition of the biting behavior induced by intrathecal injection (i.t.) of glutamate (175 nmol/site), alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA; 135 pmol/site), (+/-)-1-aminocyclopentane-trans-1,3-dicarboxylic acid (trans-ACPD; 50 nmol/site) and substance P (SP, 135 ng/site). Tramadol injected by the i.t. route (25-400 nmol/site) also produced inhibition of glutamate-, AMPA-, trans-ACPD- and SP-induced biting response. Pretreatment with tramadol by the i.p. and i.t. routes had no significant effect against the kainate- and N-methyl-D-aspartic acid (NMDA)-mediated biting response in mice. Copyright 2009 S. Karger AG, Basel.