Brain - For years police and psychologists have been trying to get
inside voilent minds.Now theyâ€™re getting closer than ever. (12/17/02)
and Socializing - Do you eat or need to be around people when youâ€™re
stressed? Scientists are studying the nerve cells of tiny worms to find
out why. (12/10/02)
Elsewhere on the web
Anger Before It Controls You - APA
Management - movie trailer
Why do some people get angry or anxious about the smallest things?
As this ScienCentral News video reports, it could be because of a missing gene
that affects their brain.
Itâ€™s normal for us to feel angry or anxious. They are normal behaviors
that help us respond to “a challenging or threatening environment”,
Evan Deneris, professor of neuroscience at Case
Western Reserve University. But, there are limits. He cautions, “if
anxiety and aggression become excessive then that will be fairly counter-productive
and prevent normal social interactions.”
Deneris and his colleagues have been studying the issue. They report that they
have found a gene that regulates normal levels of anxiety and aggression.
In a study published in the journal Neuron,
the researchers explain that when the gene called PET-1 is removed or “knocked-out”
in mice, the mice display a greater level of anxiety and aggression as adults
than do normal animals.
Deneris and colleagues had found earlier that the PET-1 gene was active only
in a certain kind of nerve cell or neuron in the brain that produced
Serotonin is a brain chemical that acts as a neurotransmitter or chemical
messenger between nerve cells. Serotonin is also important for influencing
many neural circuits that control behaviors such as anxiety, aggression, perception,
learning, memory, sleep-wake patterns, and other emotions and moods. People
who do not produce enough serotonin can suffer from mood disorders like depression
The chemical is so important; we start making it even before we are born. Deneris
says, “In humans, serotonin neurons first appear roughly in the middle
of the first trimester.”
To learn exactly what was going on inside the brain, Deneris and his team chose
to study mice. Despite their size, mice have a lot in common with people,
especially where their genes are concerned.
They specially bred mice without the PET-1 gene, and studied their serotonin
neuron development. They found that most of the serotonin neurons were missing
and the few that did remain were abnormal. “So in the absence of this
gene the entire serotonin system is defective,” says Deneris. And according
to him that leads to, “low levels of serotonin throughout the developing
adult brain in the mutant mice”.
The researchers also actually watched both the genetically modified mice and
the normal mice to see how they behave. In one test they put an unfamiliar
mouse in with the test mouse. Then, they watched how each mouse behaved. They
found the normal mice explored and investigated the intruder by sniffing and
chasing it around the cage. Sometimes, they even attacked the intruder but
they would normally “wait many minutes before attacking and some of
them would never attack”, says Deneris.
However, he says, the mice without the gene “would attack within ten
seconds of being introduced to the intruder mouse.” Also, the attacks
were more severe and happened more often.
In another test, the researchers measured the amount of time the mice spent
in open, unprotected areas of a test chamber compared to closed, protected
areas. Deneris says its normal for a mouse to spend most of its time in the
protected area to avoid threats, but that it also has a natural tendency to
want to explore. They found the modified mice never ventured into the unprotected
areas. Instead they remained exclusively in the protected areas. To Deneris
this suggests the modified mice are more anxious.
Humans have a gene that, according to Deneris, “is nearly identical to
the PET-1 gene” found in the mouse. However, he cautions they donâ€™t
yet know whether the human version functions in the same way as the mouse
He says, “given the strong similarities between the serotonin system
in the mouse and the serotonin system in the human, we would not be surprised
if the human version of PET-1 is performing a similar function in the human
brain.” He notes that these mice without the gene could be used to learn
even more. For instance, he says they could be used as a new and novel animal
model for screening possible new drugs and treatments for aggression and anxiety.
Also, they could be used for studying psychiatric disorders that involve the
This study was funded by the National
Institute of Mental Health.