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Help for aggression linked to MAOA gene mutation?
Researchers believe the dis-covery of genetic influences on aggression
will open the door to effective treatments, and a new animal study is
already pointing toward a novel gene therapy for one tentatively-
identified "aggression gene."
In 1993, H. G. Brunner and colleagues reported on a large Dutch
family in which males exhibited extreme aggressive tendencies and
borderline mental retardation. The researchers found that the impulsive,
aggressive males in this family have a mutation in the gene coding for
the enzyme monoamine oxidase A (MAOA), which metabolizes several
neurotransmitters
(see related article, Crime Times, 1995, Vol. 1, No. 3, Page 1).
Separate research has shown that mice deficient in MAOA also show
high rates of aggression.
Studying mice genetically engineered to be MAOA-deficient, Jean
Shih and colleagues tested the effects of ginkgo biloba, a common herbal
remedy that appears to have complex effects on neurotransmitters. The
researchers note that aggressive mice deficient in MAOA have abnormal
brain levels of the neurotransmitters serotonin and norepinephrine.
Shih et al. injected one group of MAOA-deficient mice with water-
soluble ginkgo biloba, and another with a placebo solution. After 10
minutes, each mouse was placed in a cage with another mouse and
observed.
"The effect of ginkgo biloba on aggression was remarkable," the
researchers say. "When 0.1 ml of ginkgo biloba was administered to
MAOA knockout mice, their aggressive behavior in resident-intruder
confrontations was reduced significantly." The substance had no effect
on the mice's nonsocial, investigative, defensive, or movement
behaviors, indicating that effects were not due simply to sedation.
Examining the brains of MAOA-deficient mice following ginkgo
biloba administration, Shih et al. found evidence that the treatment may
work by altering serotonin function. The researchers say future studies
will be necessary to determine the reason why ginkgo biloba treatment
was so effective in reducing aggression, but suggest that ginkgo biloba
"may be developed as a novel anti-aggressive agent."
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"Ginkgo biloba abolishes aggression in mice lacking MAOA," Jean C.
Shih, Kevin Chen, Michael J. Ridd, and Isabelle Seif, Antioxidants
and Redox Signaling, Vol. 2, No. 3, 2000, 467-71. Address: Jean
Chen Shih, University of Southern California, Department of Molecular
Pharmacology and Toxicology, School of Pharmacy, Room 528, Los
Angeles, CA 90089, jcshih@hsc.usc.edu.
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