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http://psychcentral.com/news/200 ... son%E2%80%99s-risk/
Nicotine Treatments May Lower Parkinson』s Risk
By: Psych Central News Editor
on Tuesday, Aug, 8, 2006
Reviewed by: John M. Grohol, Psy.D.
on Tuesday, Aug, 8, 2006
Emerging research suggests that nicotine treatments
protect against the brain damage found among
individuals with Parkinson』s disease. The finding
confirms the observation that the incidence of
Parkinson』s among smokers is 50 percent less than the
general population.
While smoking is not condoned, the finding in
laboratory animals that nicotine somehow promotes the
survival of dopamine-producing cells, could someday
lead to use of nicotine as an early treatment for
Parkinson』s disease.
The research was conducted in laboratory animals
treated with MPTP, an agent that produces a gradual
loss of brain function characteristic of Parkinson』s.
Experimental animals receiving chronic administration
of nicotine over a period of six months had 25 percent
less damage from the MPTP treatment than those not
receiving nicotine.
This protective effect may explain the lower incidence
of Parkinson』s disease among smokers. The results
also suggest that nicotine may be useful as a
potential therapy in the treatment of early-stage
Parkinson』s patients.
The five-year study was conducted by researchers at
The Parkinson』s Institute, an independent, non-profit
research institute located in Sunnyvale, California.
The study results are published in an on-line early
release in the Journal of Neurochemistry
(doi:10.1111/j.1471-4159.2006.04078.x)
Parkinson』s disease is a progressive,
neurodegenerative disease caused by the death of small
clusters of cells in the midbrain. The gradual loss of
these cells results in reduction of a critical
transmitter called dopamine, the chemical messenger
responsible for normal movement.
「While we would never recommend that people smoke,
these results suggest that nicotine promotes the
survival of dopamine-producing cells in animals with
no overt Parkinson』s symptoms,」 said David A.
Schwartz, M.D., director of the National Institute of
Environmental Health Sciences, the federal agency that
provided funding for the study. 「These findings also
have implications for its use in slowing the
progression of Parkinson』s.」
Most of the research on tobacco has focused on its
detrimental health effects. However, studies conducted
over the last 40 years show that the incidence of
Parkinson』s disease is about 50 percent less in
smokers than in the general population. 「These
studies were giving us clues that something in the
smoke was reducing the incidence of Parkinson』s,」
said Maryka Quik, Ph.D., a senior research scientist
with The Parkinson』s Institute and lead author on the
study.
Based on these findings, the researchers wondered what
compound in cigarette smoke could be causing this
effect. 「We decided to focus our attention on
nicotine because studies have shown that nicotine
stimulates the release of dopamine in the brain region
that is associated with Parkinson』s,」 said Quik.
To test their theory, the researchers treated
experimental animals with MPTP, an agent that
selectively destroys the dopamine-producing brain
cells. Half of the animals also received a low-dose
administration of nicotine over a six-month period.
During this time, the nicotine dose was gradually
increased to a level typically found in cigarette
smoke.
The test results showed that animals receiving only
the MPTP suffered a 75 percent loss of function in
their dopamine-containing brain cells. When the
researchers tested the animals that had received both
MPTP and nicotine, the damage in the dopamine cells
was only 50 percent. 「The results suggested that the
nicotine treatment had reduced the cell damage by 25
percent,」 said Quik.
While there is no immediate explanation for this
effect, the researchers believe the nicotine may
stimulate the release of naturally occurring proteins
called growth factors that play a key role in nerve
cell growth and repair. 「It is also possible that the
nicotine may activate the immune system to protect the
cells from MPTP-induced damage,」 said Quik.
According to Quik, Parkinson』s disease symptoms only
start to develop when 80 to 90 percent of dopamine in
striatal nerve terminals is depleted. 「This means
that a reduction in terminal damage from 80 to 60
percent can mean the difference between having disease
symptoms and being symptom-free,」 said Quik.
While treatments currently available for Parkinson』s
disease are limited to the day to day relief of
symptoms, nicotine may someday be used to reduce or
even prevent the progression of the disease. 「With
current symptomatic therapies, the progress of the
disease is not halted and, symptoms become worse and
more difficult to control,」 said Quik. 「With
neuroprotection, a patient could receive treatment
that would halt the disease progress and prevent
symptoms from getting worse.」
[ 本帖最後由 新鮮人 於 2006-12-24 02:35 編輯 ] |
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