Effects of Chronic Stress and Acute Morphine Exposure on Spatial Memory in Rats of Different Ages

Objective: To study the effects of chronic stress and acute morphine exposure(2mg/kg) on spatial memory in 4-and 10-week-old rats.Methods: Elevated platform stress protocol was established.Morris water maze was used to observe the effects of acute morphine exposure on spatial memory in 4-and 10-week-old stressed rats.Results: ①4-week-old rats: Rats of morphine group spent significantly less time in the target quadrant(TA) than those of control group(P0.05).Time in the target quadrant did not differ in chronic stress group and chronic stress and morphine group compared with control(P 0.05).②10-week-old rats: Rats of chronic stress group and chronic stress and morphine group spent significantly more time in the target quadrant than those of control group(P0.05);Time in the target quadrant did not differ in morphine group compared with control group(P0.05).③Comparison between 10-week-old rats and 4-week-old rats: 10-week-old rats in chronic stress group,chronic stress and morphine group and morphine group spent significantly more time in the target quadrant than that of 4-week-old rats in the same groups,respectively(P0.05).Time in the target quadrant did not differ in control group between 4-week-old rats and 10-week-old rats(P 0.05).Swimming speed did not differ in all groups of 4-or 10-week-old rats(P 0.05).Conclusion: ①Chronic stress induces enhancement of memory retention in 10-week-old rats and has no effect on memory retrieval in 4-week-old rats.It shows difference between two age groups.②Morphine in the dose of 2mg/kg induces impairment of memory retention in 4-week-old rats and has no effect on memory retention in 10-week-old rats.It shows difference between two age groups.③Chronic stress and morphine has no effect on memory retention in 4-week-old rats and induces enhancement of memory retention in 10-week-old rats.It also shows difference between two different ages.