Background: We previously reported that oral morphine dependence facilitated formation of spatial learning and memory in rats. In the current study we examined the long lasting effects of morphine on above mentioned phenomena in withdraw animals.
Materials & methods: In this study male rats received morphine sulfate (in dependent and withdrawal groups) or sucrose (in control group) in drinking water for 30 consecutive days. Morris water maze (MWM) studies were performed from day 26 to 30 (in control and dependent animals) during morphine or sucrose application or from day 21 to 25 (in withdrawal group) after morphine elimination. Spatial learning and memory parameters were subjected to the ANOVA.
Results: Data showed that spatial learning indices (escape latency, distance swam to the platform and swimming speed) and also spatial memory index (percentage of time spent in target quadrant) in dependent and withdrawal animals are better than that in control ones.
Conclusion: Oral morphine dependence has long lasting facilitatory effect on formation of spatial learning in rats. The mechanism(s) underlying phenomenon remain to be elucidated.