Fig. 1: Intrathecal administration of l-CDL attenuates morphine tolerance and antinociceptive effects.

Rats and mice were examined daily with Von Frey filaments and the tail-flick assay, respectively. Data are presented as percentages of the maximal possible effect (% MPE). The analgesic effect of morphine was decreased after the chronic morphine treatment, indicating the development of morphine tolerance. a l-CDL attenuated morphine tolerance in TCI rats at nonnarcotic analgesic doses. b The analgesia was further reported as area under the curve (AUC) units. Data are presented as means ± SE. n = 6, *P < 0.05, **P < 0.01, #P < 0.05, ##P < 0.01 compared with the morphine group. c l-CDL attenuated the development of morphine tolerance and did not affect the pain threshold in naïve mice. d The analgesia was further reported in AUC units. Data are presented as means ± SE. n = 12, *P < 0.05, **P < 0.01, compared with the morphine group