The effect of curcumin pre-treatment on morphine-induced inhibitory memory impairment and nitric oxide level in rat

Curcumin, as a polyphenolic compound in turmeric plant, has a neuroprotective effect in the improvement of learning and memory. Curcumin has interaction with diverse molecules, e.g., nitric oxide (NO). The present study dealt with the effect of curcumin pre-treatment on morphine-induced inhibitory memory impairment and nitric oxide metabolites (NOx) level in rat. In this experimental study, rats (n=40) were divided into four groups (each group, 10 rats) and their memory was evaluated in an inhibitory memory apparatus: Control (saline gavage for 35 days+post-training saline (i.p.)); Curcumin (curcumin gavage (10 mg/kg for 35 days)+post-training saline (i.p.); Morphine (saline gavage for 35 days+post-training morphine (7.5 mg/kg/i.p.)); Curcumin+Morphine (curcumin gavage (35 days)+post-training morphine (i.p.)). In all groups, the memory of animals in the second day (test) was reported as the time delay (Sec.) to enter the dark chamber. The locomotor activity was evaluated using the open field. After behavioral tests, the brain of animals was removed under deep anesthesia for evaluating the NOx level using the Griess method. The time delay to enter the dark chamber in Morphine and Morphine+Curcumin groups were decreased (P<0.001) and increased (P<0.01), compared to Control and Morphine groups, respectively. Tissue NOx levels in Morphine and Morphine+Curcumin groups were decreased (P<0.05) and increased (P<0.001), compared to Control and Morphine groups, respectively. Locomotor activity in open field did not show a significant difference in four groups (P>0.05). Curcumin improves the morphine-induced inhibitory memory impairment in rat, probably via the NO signaling pathway.