Preventive effects of fixed and progressive forced exercises on memory and brain electrical activity in morphine-addicted rats

Abstract

Exercise and addiction influence brain functions. The preventive effects of fixed and progressive forced exercises on both brain functions and body weight were investigated in morphine-addicted rats. Thirty-five rats were allocated to control, morphine, fixed exercise-morphine, and progressive exercise-morphine groups. Forced exercise was applied 1h/day for 21 days with morphine sulfate administered at doses of 10, 20, 30, 40, and 50 mg/kg for 5 consecutive days. The 50 mg/kg dose was repeated over the five subsequent days. Brain performance was evaluated using the passive avoidance test and EEG recordings. The passive avoidance test revealed no significant changes in brain functions (namely, latency, total dark stay time, and number of times entering the dark compartment). Compared to the control, the morphine group exhibited significantly lower alpha and beta waves but significantly higher delta and theta ones. Compared to the morphine group, the progressive and fixed exercise-morphine groups exhibited significant changes in their passive avoidance performance and only in the alpha wave of their EEG recordings. Progressive exercise improved learning, memory, and memory consolidation but reduced locomotor activity whereas fixed exercise affected EEG recordings in the addicted subjects. Clearly, different (fixed or progressive) exercise models produced different changes in brain functions.

Key words
addiction; brain waves; exercise; memory; morphine; rat