Re: OT- endorphins

[Guest guest]

Thank you, Kathy. Very interesting. It would be nice to have this done on humans to see if the results are the same and to determine what "moderate" levels would truly be considered, if it applied in the same manner. Victor.Kathy <kathypnrs@...> wrote: Moderate Exercise Best for Brain Source: NewsRx.com Exercise is good for your physical health; we have known this for a long time. We also know that physical activity is good for the brain and alleviates depression and stress. What's more, training improves both memory and learning capacities. On the other hand, exaggerated exercise, when the body doesn't have a chance to recover, has a negative effect, with fewer brain cells as a result. This is the subject of a dissertation from the Sahlgrenska Academy at Goteborg University in Sweden. Moderation is best, in other words. Biologist Naylor arrived at this by studying rats running in a treadmill. Rats that were allowed to run the treadmill for 9 days acquired 5 times as many new stem cells in the part of the brain called the hippocampus compared with rats in a control group that did

not run at all. Four weeks after 4 weeks after the treadmill had been removed from the cage, about a third of the new cells were still there and had developed into functioning nerve cells. The hippocampus is a part of the brain that is important for the regulation of stress reactions, but also for memory and learning. Naylor confirmed that these rats actually were better learners after their exercise by running memory and learning tests on them. The test had the rats swim in a round basin that had one place where they could get up out of the pool. The rats that had exercised learned more quickly than those who hadn't where they should swim to get out of the water. A third group of rats were allowed to run on the treadmill as much as they wanted for 24 days. Surprisingly, these rats increased their amount of running from 6 kilometers a day to as much as 20 km a day. "Just why these rats ran more and more, I can't say, but they seem to like it. Maybe

they develop an addiction of some sort. I plan to study this in the future," says Naylor. But even if the rats run a lot because they like it, this had no positive impact on the number of cells in the brain. On the contrary, they developed only half as many new cells in the hippocampus as the ones that didn't exercise at all." "What's interesting is that if the over-exercising rats were left to rest for a few weeks, more than half of their newly-formed cells survived, which is more than twice as many as in rats who didn't exercise. But since there were fewer new cells from the beginning in the over-exercised rats, the ultimate result was largely the same number of cells in both groups anyway. In other words, the brain seems to find a way to compensate for the fact that fewer cells are formed when rats run too much." Why is physical exercise in moderation good for the brain but too much not? This probably has to do with endorphins, the body's own morphine, and

the stress hormone corticosterone. Endorphins are released with physical exercise, and Naylor has shown that it is endorphins that stimulate the new generation of cells in the hippocampus: when he blocked the effect of endorphins in the rats, the increase in new cell formation did not occur. In rats that exercise too much it is probably the effect of corticosterone that takes over. In previous studies it has been shown that coricosterone, which is released with stress, and stress itself both decrease the new formation of cells in the hippocampus in rats. In humans the effect of long-term stress is a shrinking of the hippocampus, which may be the result of decreased generation of new cells. "It isn't easy to translate what is moderate exercise for a rat into what is just right for us humans. There are recommendations that say it is optimal for your health to exercise for 35 minutes 4 to 5 days per week at 60% of your maximum pulse [heart rate]. It is hard to

say whether this is also optimal for mental health. There is research that indicates that elite athletes can be negatively affected by long and intensive periods of training. We everyday exercisers don't train like that, but if the physical stress is too great, the same thing can no doubt happen to us," says Naylor. ---- This article was prepared by Biotech Week editors from staff and other reports. Copyright 2005, Biotech Week via NewsRx.com. To see more of the NewsRx.com, or to subscribe, go to http://www.newsrx.com. © 2004 NewsRx.com. .;;©Copyright 2005, Biotech Week via NewsRx.com __________________________________________________