Anti-depressants Often Fail

NewsDaily: Study in mice shows why antidepressants often fail
NewsDaily (2010-02-12) -- Antidepressants fail to help about half of the people who take them, and a study in mice may help explain why. ... > read full article

For the study, Hen and colleagues needed to reach serotonin receptors in just the right part of the brain.

To do this, the team used mice that were genetically altered to have fewer serotonin receptors only in the region where the serotonin-producing raphe neurons are located.

Once the team had mice that had different levels of serotonin receptors in different parts of the brain, they did a behavior test that assesses boldness when mice get food in a brightly lit area.

Mice on antidepressants usually become more daring, but the drugs had no such effect on mice with surplus serotonin receptors.

"The most dramatic finding is that the mice that have high levels of receptors in these serotonin neurons do not respond to fluoxetine or Prozac," Hen said.

But when they reduced the number of these receptors -- or molecular doorways -- they were able to reverse the effect, he said.

"By simply tweaking the number of receptors down, we were able to transform a non-responder into a responder," Hen said. At least 27 million take antidepressants in the United States, nearly double the number that did in the mid-1990s