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By Kathleen Doheny - HealthDay Reporter. Experts have long suspected that one way antidepressants such as Prozac, Paxil and Zoloft dispel depression is by stimulating the growth of new brain cells.

Now, researchers say they've zeroed in on just how that happens.

"It was clear that this generation of new neurons is important for the action of antidepressants," explained lead researcher Grigori Enikolopov, an associate professor at Cold Spring Harbor Laboratory in Cold Spring Harbor, N.Y.

His team report the findings in this week's online edition of the Proceedings of the National Academy of Sciences.

The researchers decided to look at how the use of selective serotonin re-uptake inhibitor (SSRI) antidepressants -- the widely used class of drugs that includes Celexa, Paxil, Prozac and Zoloft -- might spur brain cell growth.
To do so, they tracked the way in which stem cells -- undifferentiated cells that can grow into specialized cells -- became neurons in a special mouse model given the antidepressant Prozac (fluoxetine).

"Stem cells in the brain go through several steps before they become neurons," Enikolopov said. Examining the cascade of events, his team found that "cells which are born from the stem cells, called amplifying progenitors, are the cells being targeted by Prozac," he said. According to Enikolopov, Prozac zeroes in on these amplifying progenitors and increases their numbers. Within three to four weeks, his team noticed an increased number of mature neurons.

The Cold Spring researchers noted that about four years ago, other researchers found that animals that received Prozac showed a rise in neuron growth. Then, about two years ago, other experts found that this generation of new neurons is necessary for the drug to achieve its behavioral effect of lifting depression, Enikolopov said.

He believes the latest finding is another piece to add to the puzzle of how SSRI antidepressants work. However, it does not provide the entire answer. "What happens between having more neurons and decreasing depression, the changing of mood -- that is unanswered," he said.

The team of inventors behind Prozac was lead by Ray Fuller at Eli Lilly Company and Bryan Molloy and David Wong were both members of the Eli Lilly Company research team.
Prozac first went on the market in 1987 in the United States as the first SSRI. These medications selectively target serotonin, inhibiting its reabsorption into the cell so there is more available...MORE..
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SCIENTISTS FIND TREATMENT FOR HUNTINGTON'S DISEASE WITH PROZAC:
Howard Florey Institute scientists in Melbourne have found that fluoxetine (commonly marketed as prozac) not only improves depression in Huntington's disease, but also improves learning and memory.

Dr. Anthony Hannan and his team also found that fluoxetine restores the brain's process of neurogenesis - the birth of new neurons - to normal levels, which helps delay the onset of the inherited fatal disease.

People with Huntington's disease have progressive motor problems, cognitive deficits (dementia) and psychiatric symptoms (the most common is depression) that usually start to appear in mid-life. There is no cure and death usually results within 10 to 20 years of symptom onset, or faster in the childhood-onset form of the disease. The disease is caused by a mutation in a single gene and when this defective gene is passed from parent to child, 50 percent of the offspring will inherit the disorder, which can be detected by genetic testing.

Dr Hannan said this discovery was an important step in developing effective treatments to delay the onset of symptoms and the progression of Huntington's disease...MORE... Read the Full Story Here

PROZAC REDUCES DISEASE ACTIVITY IN MS PATIENTS:
(HealthDay News) -- Prozac may help reduce disease activity in people with the relapsing remitting form of multiple sclerosis (MS), a new study suggests...MORE...
Prozac Reduces Disease Activity in MS Patients - Read the Full Story Here