Branford-based Neurogen Corp. appointed Stephen R. Davis president, effective immediately. William H. Koster, previously president and CEO, will remain as CEO of the company, though Davis has been selected as his future successor. Previously, Davis, who has been with the company since 1994, was executive vice president and COO. He has also held positions with Milbank, Tweed, Hadley and McCloy and Aurthur Anderson & Co. Davis has a B.S. in accounting from Southern Nazarene University and a J.D. from Vanderbilt University.