Rigorous physical exercise before binge drinking may reduce brain damage in adolescents.
Monkeys are much like humans. If you leave them alone with alcohol, some of them are sure to get drunk quickly. But that’s a useful trait, because then you can study their brains easily. Scientists at the Scripps Research Institute near San Diego in the US did exactly that with adolescent monkeys, and came to some disturbing conclusions.
Chitra Mandyam and her colleagues at the Scripps Institute were investigating the effects of binge drinking among adolescents. They let the monkeys drink for an hour every day for 11 months. They then stopped the alcohol supply for two months, after which they examined the brains of the animals. The monkeys showed permanent damage in the hippocampus, an area that is crucial to the formation of new memory.
Adolescence — whether in rats, monkeys or humans — is a period of intense physical and mental change. “It is a vulnerable period,” says Mandyam.
According to several studies, binge drinking is increasing among adolescents. Over 60 per cent of these youngsters are at risk of developing brain disorders. It is thus necessary to understand how alcohol damages the brain, how lasting the damage is, and what can be done to reverse it.
“There have been several studies on rodents,” says Mandyam. “But this is the first time we studied binge drinking in monkeys.” There are many advantages of studying the phenomenon in monkeys. The animals are genetically similar to human beings, they drink like humans, and their brains are affected in a manner similar to that in humans.
Neurons in the hippocampus are generated the same way in monkeys as in humans. Since it is difficult to get the brains of adolescent humans for post-mortem, monkeys form the closest approximation for studying the effect of alcohol on adolescent humans.
Scientists at the Scripps Institute first selected a set of monkeys who liked to drink alcohol, and then divided it into two groups. One group was allowed to drink for 11 months and the other did not get to drink. Neurons in the hippocampus of the animals that drank had degenerated when seen even after two months of abstinence. The level of stem cells in the brain also decreased, suggesting the brain had less capacity to repair the damage.
The hippocampus is an important area of the brain that is involved in several functions like spatial memory formation, executive functioning and short-term and long-term memory formation. If damaged during adolescence, it could affect an individual’s functioning for a lifetime. This is particularly true if the stem cells are damaged. Mandyam’s study showed that as much as 90 per cent of the stem cells in the hippocampus could be damaged by binge drinking.
So the next question is: what can we do to reverse the damage? The brain is known to be very plastic, but can we invoke this plasticity when the stem cells in the hippocampus are damaged? There are no studies of monkeys, but those of rats suggest that one may be able to control this damage partly.
One particular study by Kimberly Nixon and her colleagues at the University of Kentucky in the US has shown that exercise before drinking may reduce the damage to a certain extent.
Nixon made rats exercise voluntarily for 14 days before four days of intense drinking. When the brains of the rodents were examined after that, they showed reduced damage compared with rats that did not exercise. However, we cannot necessarily conclude that all alcohol damage is reversible. “We do not know the threshold levels alcohol begins to be toxic,” says Nixon. “There is old data saying that over 50 per cent of alcoholics have persistent cognitive defects they never recover from.”
There may be several reasons why exercise shows reduced damage. It could be that the brain cells form new connections to compensate for lost cells. Abstinence and the passage of time may help the brain recover a bit. But we still do not know the many ways in which alcohol affects the brain.
However, we do know two things: binge drinking can permanently damage parts of the brain. And a period of exercise before drinking can prevent or at least reduce brain cell death.
Source : The Telegraph ( Kolkata, India)
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