发信人: yanan (花自飘零水自流), 信区: Biology
标 题: Arvid Carlsson_ dopamine and parkinson's disease
发信站: The unknown SPACE (Mon Oct 9 15:03:12 2000), 站内信件

ARVID CARLSSON

Dopamine - an important transmitter
Arvid Carlsson performed a series of pioneering studies during the
late 1950's, which showed that dopamine is an important transmitter
in the brain. It was previously believed that dopamine was only a
precursor of another transmitter, noradrenaline. Arvid Carlsson
developed an assay that made it possible to measure tissue levels
of dopamine with high sensitivity. He found that dopamine was
concentrated in other areas of the brain than noradrenaline,
which led him to the conclusion that dopamine is a transmitter
in itself. Dopamine existed in particularly high concentrations
in those parts of the brain, called the basal ganglia, which are
of particular importance for the control of motor behavior.
In a series of experiments Arvid Carlsson used a naturally
occurring substance, reserpine, which depletes the storage of
several synaptic transmitters. When it was given to experimental
animals they lost their ability to perform spontaneous movements.
He then treated the animals with L-dopa, a precursor of dopamine,
which is transformed to dopamine in the brain. The symptoms
disappeared and the animals resumed their normal motor behavior.
In contrast, animals that received a precursor of the transmitter
serotonin did not improve the motor behavior. Arvid Carlsson also
showed that the treatment with L-dopa normalized the levels of
dopamine in the brain.

Drugs against Parkinson's disease
Arvid Carlsson realized that the symptoms caused by reserpine
were similar to the syndrome of Parkinson's disease. This led,
in turn, to the finding that Parkinson patients have abnormally
low concentrations of dopamine in the basal ganglia. As a
consequence L-dopa was developed as a drug against Parkinson's
disease and today still is the most important treatment for the
disease. During Parkinson's disease dopamine producing nerve cells
in the basal ganglia degenerate, which causes tremor, rigidity and
akinesia. L-dopa, which is converted to dopamine in the brain,
compensates for the lack of dopamine and normalizes motor behavior.

Antipsychotic and antidepressive drugs
Apart from the successful treatment of Parkinson's disease Arvid
Carlsson's research has increased our understanding of the mechanism
of several other drugs. He showed that antipsychotic drugs, mostly
used against schizophrenia, affect synaptic transmission by blocking
dopamine receptors. The discoveries of Arvid Carlsson have had great
importance for the treatment of depression, which is one of our most
common diseases. He has contributed strongly to the development of
selective serotonin uptake blockers, a new generation of
antidepressive drugs.

--
紫霞问：“是不是一到夏天，满山就会开满紫色的木逍花？”

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