How exercise can prime the brain for addiction
Baku, April 14 (AZERTAC). The study, conducted by researchers at the Beckman Institute for Advanced Science and Technology at the University of Illinois in Urbana-Champaign, began by dividing male mice into those that had or did not have running wheels in their cages. All of the mice were injected with a chemical that marks newly created brain cells. The animals then sat in their cages or ran at will for 30 days. Afterward, the mice were placed in small multiroom chambers in the lab and introduced to liquid cocaine. They liked it. Researchers frequently use a model known as “conditioned place preference” to study addiction in animals. If a rodent returns to and stubbornly plants itself in a particular place where it has received a drug or other pleasurable experience, then the researchers conclude that the animal has become habituated. It badly wants to repeat the experience that it associates with that place. All of the mice displayed a decided place preference for the spot within their chamber where they received cocaine. They had learned to associate that location with the pleasures of the drug. All of the mice had, essentially, become addicts. Then the researchers cut off the animals` drug supply and watched how long it took them to stop scuttling to their preferred place. This process, known as “extinction of the conditioned place preference,” is thought to indicate that an animal has overcome its addiction.
The researchers noted two distinct patterns among the addicted exercisers. The formerly sedentary mice that had begun running only after they became addicted lost their conditioned place preference quickly and with apparent ease. For them, it appeared relatively easy to break the habit. Those that had been runners when they first tried cocaine, however, lost their preference slowly, if at all. Many, in fact, never stopped hanging out in the drug-associated locale, a rather poignant reminder of the power of addiction.
So, the researchers propose, the animals that had been running before they were introduced to cocaine had a plentiful supply of new brain cells primed to learn. And what they learned was to crave the drug. Consequently, they had much more difficulty forgetting what they`d learned and moving on from their addiction.
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