Fig. 3

NMDAR activation potentiated morphine-induced pruritus and decreased its analgesia. a Morphine-induced pruritus (M 0.1 μg or M 0.25 μg) was significantly increased by 0.005 nmol NMDA. b NMDA (0.005 nmol) significantly increased the total number of scratches in 30 min that was induced by 0.5 μg morphine. c Time course of the effects of intrathecal morphine and intrathecal NMDA on morphine-induced analgesia over 2 h post-injection. NMDA injection significantly reduced the time course of analgesia induced by intrathecal morphine at either 0.1 μg or 0.25 μg. d The effect of ketamine and ifenprodil on AUC calculated based on %MPE in (c). Compared with the AUCs in the morphine groups (M 0.1 μg or M 0.25 μg), the AUCs in the morphine + NMDA groups were both significantly reduced. Error bars represent SEM. *: p<0.05, compared to the NS group. †: p<0.05, compared to the 0.1 μg morphine group. ‡: p<0.05, compared to the 0.25 μg morphine group