Laboratory animals that exercise have a harder time giving up their cocaine habits compared to their couch potato peers, according to a new study from the University of Illinois at Urbana. Lead author Justin Rhodes was quick to point out that his work should not keep people from exercising, especially if they are recovering from addictions.
Dr. Rhodes and his colleagues at the Beckman Institute for Advanced Science and Technology started off with two groups of laboratory mice. One group had exercise wheels and was allowed to exercise as much as they wanted, and the others did not exercise. Then all the mice were exposed to cocaine, and they quickly developed a preference for the place in their cages where they could receive the drug. They associated that place with the pleasure of the drug and just as quickly became addicted. Some of the inactive animals were allowed to exercise, as were all the animals that had exercised originally.
The group that began to run only after they became addicted to cocaine had little trouble breaking their drug habits. However, those who had already been runners when they tried cocaine had difficulty losing their preference for the place in their cages where they got their drug, and many never stopped going there.
"There is good news and maybe not-so-good news about our findings," said Dr. Rhodes.
The results could mean that it would be harder for a person used to exercising to recover from addictions. Dr. Rhodes explained why he thought this might be true. The brains of the animals that exercise had more new cells, especially in a region of the brain critical for learning. It could be that having more brain cells enabled them to learn to crave the drug more efficiently than the others, and to have more problems forgetting what they learned.
Dr. Rhodes pointed out that other studies have shown that since exercise stimulates the reward centers in the brain, it can almost become a substitute for drugs in some people. They can achieve "runner’s highs," for example, and not crave the effects of psychoactive substances.
He said this study does not tell the whole story of the relationship between exercise and addiction because it looks that only one narrow aspect of it.
The study appears in the European Journal of Neuroscience.