THE EFFECTS OF EXERCISE ON THE ORAL CONSUMPTION OF MORPHINE AND METHADONE IN RATS

Endogenous opioid peptides have been hypothesised to play a regulatory role in exogenous opiate agonist dependence. It was hypothesised that exercised rats would demonstrate increased beta-endorphin (beta EP) l evels and decreased exogenous opiate intake. After providing morphine or methadone as their sole liquid, drug preference levels were determi ned by amounts of exogenous opiate consumed when rats were offered a c hoice between drugged and nondrugged solutions. Treatment animals were exercised in a treadmill and were found to consume significantly less exogenous opiate than control animals. Plasma, pituitary, and whole b rain beta EP levels were nonsignificantly higher in exercised animals. Differences were observed in the drug ingestion patterns of morphine- and methadone-exposed rats.