Researchers have found the first direct evidence of a specific
enzyme that controls the production of serotonin in the brain. Various
types of this serotonin enzyme found in mice have been found to
strongly affect brain levels of the chemical messenger which is
linked to sleep, appetite, emotions and mood -- many basic behavioral
and physiological functions. Scientists believe this discovery will
help them better understand psychiatric disorders and learn how
to treat them.
Serotonin, a neurotransmitter of sorts, is a chemical that uses
a neuron to trigger nerve impulses in its neighbors. As such, it
can greatly affect brain function and behavior.
Researchers believe these findings can offer new insights into
the role of this enzyme as well as the accompanying gene that encodes
it which could better explain animal behaviors and human psychiatric
disorders. Low serotonin levels are blamed for many disorders, including
depression, anxiety, post-traumatic stress disorder and attention
deficit hyperactivity disorder.
This enzyme could also affect a patient's
response to serotonin re-uptake inhibitors (SSRIs):
- Paxil (paroxetine)
- Zoloft (sertraline)
- Prozac (fluoxetine)
Before this discovery, scientists believed tryptophan hydroxylase
(Tph1) to be the sole enzyme governing serotonin synthesis in the
nervous system. That was up to last year, when another group of
scientists found a second enzyme, tryptophan hydroxylase-2 (Tph2),
present in the brain.
When researchers screened mice for the Tph2 gene, they found two
versions that varied based on a single unit of DNA or a nucelotide.
This single difference altered the gene so it produced a variant
with different amino acid, opening the possibility that the change
could affect protein function and serotonin production. Scientists
believe this one genetic difference has a huge impact on serotonin
levels, confirming that the gene is fundamental in the synthesis
of brain serotonin.
In stark difference to inbred mouse strains, however, experts theorize
humans have many strains of the serotonin gene
Science
Daily July 9, 2004
| 