Cocaine disrupts the balance of microbes in the guts of mice, part of a cycle of waxing and waning neurochemicals that can enhance the drug’s effects in the brain. But the same chemicals may also be harnessed to prevent addiction, according to new research from the University of Wisconsin–Madison.Cocaine increases levels of a hormone called norepinephrine in users’ intestines, triggering an explosion of growth of proteobacteria, a family of microbes that includes the common and sometimes harmful bacterium E.