Depression Treatments Grow New Neurons
> 11/9/2007 2:02:30 PM

Scientists used to believe that adult brains were incapable of growing new neurons (neurogenesis). How depressing! Happily, research in the new millennia shows that people of any age can grow neurons to replace damaged ones or learn new abilities. This week, Dr. Tarique Perera found evidence that those who respond to antidepressants get better because of neurogenesis.

At the conclusion of an experiment back in May of this year, Dr. Perera got her first strong hint that at least part of the depression treatment process involves neurogenesis. Adult monkeys given electroconvulsive therapy showed neurogenesis in the hippocampus, a crucial brain region that handles learning and memory. She first checked to make sure that this new growth was not just the replacement of dying neurons, finding that not only were neurons not being killed by electroconvulsion, but that they actually received extra protection from the increased production of the BCL2 protein.

With the proof that depression treatment can cause neurogenesis, Dr. Perera set out to determine whether this growth was responsible for symptom reduction or merely an irrelevant byproduct. To do this, she first created a group of monkeys with depression by repeatedly separating them from their social groups. She then divided this group and gave half of them a placebo and half the antidepressant fluoxetine. Both depressed and control group monkeys grew new neurons in the hippocampus, but the only behavioral change occurred in the depressed group, which became less despondent. The last stage of the test exposed depressed monkeys to x-rays that destroy newly forged, and thus vulnerable, neurons but spare mature neurons. The monkeys given fluoxetine but prevented from maturing new neurons showed no remission of symptoms. This verifies the hypothesis that neurogenesis is the mechanism by which antidepressants work.

This insight will allow scientists to more effectively use current antidepressants, and to develop new ones.  It has been difficult for doctors to understand why some patients are helped by one antidepressants and others must spend months using trial-and-error until they find one that works. Now doctors can focus their attention on neurogenesis, and they have a better chance of figuring out what is preventing a particular drug from helping a particular person. It will also be easier for drug developers to find new antidepressants because they can focus on the compounds most likely to encourage neuron growth. In addition to these practical benefits, Dr. Perera's discovery is symbolically encouraging because it offers hope to those in even the most paralyzing gloom that their minds are still capable of growing towards happiness.

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