The research appears as the "Paper of the Week" in the September 17 issue of the Journal of Biological Chemistry, an American Society for Biochemistry and Molecular Biology journal.
The monoamine oxidase isoenzymes MAO A and MAO B are involved in breaking down neurotransmitters. Higher or lower than normal amounts of these isoenzymes result in irregular neurotransmitter levels, causing abnormal behavior. Realizing the connection between neurotransmitter levels and behavior, psychiatrists routinely use MAO A inhibitors as antidepressants and MAO B inhibitors for Parkinson's disease.
By making knockout mice lacking either MAO A or MAO B, Jean C. Shih, a Professor at the University of Southern California School of Pharmacy, and her collaborators previously showed how each isoenzyme functions in the body. However, up until now, scientists have been unsuccessful at making a mouse lacking both MAO A and MAO B.
This all changed when Dr. Shih and her colleague, Professor Kevin Chen, noticed that one of the mice in an MAO B knockout litter was a little different from its littermates--it had a lower body weight and was extremely hyper-reactive when approached. Wanting to figure out why the mouse was different, the scientists decided to breed the mouse and examine its offspring.
The scientists discovered that the mice not only had high levels of neurotransmitters broken down by MAO B, as would be expected in mice lacking MAO B, but also had high levels of neurotransmitters broken down by MAO A. This indicated that somehow the MAO B knockout mouse
Contact: Nicole Kresge
American Society for Biochemistry and Molecular Biology