(A) Mechanical nociceptive thresholds were evaluated before and up to 48 hours after intrathecal (i.t.) injection of quinolinic acid (QA; 0.8–80 nmol) or vehicle (saline) in WT mice (n = 5). (B) Mechanical nociceptive threshold was evaluated before and up to 48 hours after i.t. injection of QA (80 nmol) in mice pretreated with MK801 (10 nmol) or vehicle (n = 4–5). (C) Representative trace and (D) quantification of QA (5–500 μM) eliciting an inward current (n = 5) and promoting an augmentation in peak-to-peak noise variance (E, n = 5) in spinal cord neurons. (F and G) Both effects were antagonized by the NMDA antagonist DAP-5 (50 μM, n = 4). Data are expressed as mean ± SEM. *P < 0.05, **P < 0.01, ***P < 0.001 versus vehicle, treatment, or current baseline by 2-way ANOVA with Bonferroni’s post hoc test (A and B), paired 2-tailed Student’s t test (D and E), or unpaired 2-tailed Student’s t test (G).