how can serotonin be removed?   thought it was an essential brain chemical?


----- Original Message ----- 
From: "mschild" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Thursday, July 01, 2010 1:21 AM
Subject: Serotonin solves decades-old mystery in Parkinson's disease


> The study sheds light on the long term consequences of brain tissue
> transplants and may help improve future trials that consist of 
> transplanting
> cells from other sources, such as bioengineered cells or stem cells.
> Pioneering surgeries performed with aborted fetal tissue in the 1980’s in
> patients with Parkinson’s proved that the diseased brain could be 
> repaired, at
> least in some cases. The treatment aimed to replace decayed dopamine cells 
> in
> the brain’s of Parkinson’s patients. Some transplanted patients showed
> remarkable improvement but eventually the majority developed dyskinesias.
>
> The controversy surrounding the transplantation of fetal cells into adults 
> put
> an end to human trials in the United States in the late 1980’s when the 
> U.S.
> government temporarily banned fetal tissue research, though research 
> continued
> in other parts of the world. The U.S. ban was lifted in the early 1990’s, 
> but
> the cause of dyskinesias in these patients remained a mystery, and no 
> effective
> treatment has been found.
>
> Now, Marios Politis and colleagues in the United Kingdom and Sweden have
> discovered that the neurotransmitter serotonin is the culprit. Using 
> imaging
> scans and radioactive tracers, the researchers were able to visualize the
> function of different chemicals in the two patient’s brains. Taking a 
> closer
> look, they found that previously decayed dopamine neurons—a hallmark of
> Parkinson’s disease—were still restored and fully functional over a decade
> after transplantation. But Politis and colleagues also saw unexpectedly 
> high
> amounts of serotonin neurons in the transplanted tissue.
>
> The finding is puzzling because the usual dyskinesias in Parkinson’s are
> thought to be a result of dopamine action, not serotonin. The researchers
> discovered that the deceptive ability of serotonin neurons to switch to a
> different neurotransmitter—to adopt and pump out dopamine—causes the
> dyskinesias. Administering a drug to block this action almost immediately
> eliminated the dyskinesias in both patients. The authors also suggest that
> removing serotonin in any future cell-based therapies might prevent this
> crippling side effect. Recently, a new trial launched under the name 
> TRANSEURO
> plans to use fetal cell therapy to treat Parkinson's disease, with the 
> first
> surgeries planned in 2012.
>
> More information: "Serotonergic Neurons Mediate Dyskinesia Side Effects in
> Parkinson’s Patients with Neural Transplants," by M. Politis et al. 
> Science
> Translational Medicine.
>
> Provided by AAAS
>
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