Vol. 7, No. 4, 2001 Page 4
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."
"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.