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New neurons key to antidepressant effect

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Aussie news article re research done on mice and reported in "Molecular Psychiatry." The news article is subtitled:


Scientists have uncovered a vital clue which helps to explain how antidepressants work. It seems that it all depends on growing some new neurons.

After summarizing the lab study which disabled the dentate gyrus portion of brain (which "readily grows new neurons throughout adult life" according to the article) in one of the groups of mice, the article states in part:


The key discovery in Surget's research is that the antidepressant [fluoxetine] only worked if the dentate gyrus was able to generate new neurons.


To prove this was the case, the team knocked out the dentate gyrus in some of the mice before the experiment using targeted x-rays, and in these mice, fluoxetine had no effect...


...Professor Julio Licinio of the Australian National University, an expert in this field, says there has been a lot of debate about whether neurogenesis is relevant for antidepressant action.


"What is good about this study is that they have meticulously shown that neurogenesis is important," he said.


Antidepressants like Prozac are known to affect the neurotransmitter serotonin.


"When you take Prozac, the effects on serotonin are very fast - within an hour there is more serotonin in the brain," Professor Licinio said.


However, the patient's mood does not improve an hour after taking antidepressants. In fact fluoxetine takes several weeks to work, so scientists have known that there must be more involved than simply increasing serotonin.


"A very good candidate for explaining why these antidepressants take so long to work is that it takes time to grow the new neurons," Professor Licinio said.



I don't know enough about anatomy or physiology of the brain to have any opinion on whether their deductions about what occurred are correct. But thought it might be food for thought.

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Good find, Brandy! This is very important.



From Wiki --


The dentate gyrus is part of the hippocampal formation....


The dentate gyrus is thought to contribute to the formation of memories and to play a role in depression....


The dentate gyrus may also have a functional role in stress and depression. For instance, neurogenesis has been found to increase in response to chronic treatment with antidepressants. On the contrary, however, the physiological effects of stress, often characterized by release of glucocorticoids such as cortisol, as well as activation of the sympathetic division of the autonomic nervous system, have been shown to inhibit the process of neurogenesis....


Some evidence suggests that neurogenesis in the dentate gyrus increases in response to aerobic exercise....

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