Regulation of Monoamine Oxidase A during Social Defeat Stress HIGUCHIYUKI 2019 This project studied how social stress affects the expression of an enzyme (MAO-A) which degrades serotonin, a molecule which controls our mood and behavior. Using fish as an experimental animal, we measured the expression of the genes that are potentially related to the enzyme. We found that social stress affected the expression of MAO-A in the brain of fish. Also, our data show that some regulators of MAO-A were also changed by social stress.