The Serotonin Surprise | DiscoverMagazine.comGlenmullen has long suspected that drugs that alter serotonin metabolism cause profound changes in the brain. He bases his suspicion on a body of research during the last 20 years by scientists investigating another class of drugs that includes MDMA (Ecstasy) as well as fenfluramine, the diet drug recently removed from the market because of its association with heart valve problems. These drugs do more than just block serotonin reuptake; they primarily stimulate the release of large quantities of serotonin from nerve endings into the brain. The resulting flood is thought to cause the mind-altering effects of MDMA. And that flood, some scientists argue, leaves brain damage in its wake. When monkeys and rats are given high doses of serotonin releasers--up to 40 times the dose that people generally take--the microscopic architecture of their brains looks different from normal brains. The nerve fibers (axons) that carry serotonin to the target cells seem to change their shape and diminish in number--effects some scientists claim are properly understood as brain damage.