THURSDAY, April 17 (HealthDay News) -- The antidepressant Prozac has been shown to restore old brain cells to their more plastic youthful condition in animal experiments, researchers report.

The work not only provides a possible new explanation for the antidepressant activity of the medication but also raises the distant prospect that it could be used to treat other conditions caused by malfunction of brain cells, said study lead author Jose Fernando Maya Vetencourt.

"It suggests potential clinical applications for the drug in different pathologies," said Vetencourt, a researcher in neurobiology at the Scuola Normale Superiore in Pisa, Italy. One of them is amblyopia, the "lazy eye" condition in which one eye is weaker than the other, because it was not used enough in early childhood, he said.

It's much too early to say when, whether or how Prozac, whose generic name is fluoxetine, could be used in such treatments, Vetencourt said. It's also too early to say whether other members of the chemical family of antidepressants to which Prozac belongs have the same youth-restoring ability, or whether other antidepressants do the same thing, he said.

"All this needs to be validated in animal models," Vetencourt said. His study colleagues, who included researchers in Finland, have begun to study "the expression of genes which may be correlated to the functional changes," he said.

The findings were published in the April 17 issue of the journal Science.

Amblyopia was listed as a possible target, because the experiments were aimed at the brain cells governing vision. Vetencourt and his colleagues gave regular doses of Prozac to adult rats whose vision had been impaired by lack of exposure to visual images at a critical period in their early development. Tests showed changes in brain protein expression and electrical signaling typical of younger brain cells and recovery of vision by the animals.

Future experiments will try to determine whether the same treatment will have a similar effect on brain cells governing functions other than vision, Vetencourt said.

Prozac is one of the antidepressant drugs listed as selective serotonin reuptake inhibitors (SSRIs), so called because they block the activity of serotonin, a molecule that transmits signals between brain cells. There are a number of other chemical families of antidepressant drugs, also described by their activity affecting brain chemistry -- MAO inhibitors, for example.

"There have been discussions about the theory that a cause of depression is lack of growth in the brain," said Dr. Julio Licinio, chairman of psychiatry at the University of Miami Miller School of Medicine. "It used to be thought that no change could occur in the adult brain. New research has shown that there can be new growth in the brain, so the theory is that depression is caused by lack of new growth."

The new study "supports that theory in a very interesting way," Licinio said. "It both shows a potential new treatment for depression and also further supports the idea that antidepressants act because they promote growth in the brain."

And what applies to Prozac probably is true of other SSRIs and of antidepressants in general, he said. "There have been a lot of other papers showing that other antidepressants have the same property of growth in the brain," Licinio said.

More information

You can learn more about antidepressants from the U.S. National Library of Medicine.

SOURCES: Jose Fernando Maya Vetencourt, Ph.D., researcher, neurobiology, Scuola Normale Superiore, Pisa, Italy; Julio Licinio, M.D., chairman, psychiatry, Unversity of Miami Miller School of Medicine; April 18, 2008, Science

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