sentences:  In November 1983, about a year after approving aspartame, Hayes left the FDA and joined the public-relations firm Burson-Marsteller, Searle's public relations agency at the time, as a senior medical adviser.The actions of Samuel Skinner, in taking a job with a law firm retained by Searle during an investigation into Searle, and Arthur Hull Hayes, in taking a job with Searle's public relations agency following aspartame's approval, fueled conspiracy theories.Because of the approval controversy, Senator Howard M. Metzenbaum requested an investigation by the U.S. Government Accountability Office (GAO) of aspartame's approval.