RENO (AP) - Republican Sen. Dean Heller and Democratic Rep. Shelley Berkley square off in their first of three scheduled debates in Nevada's U.S. Senate race.The debate in Reno takes place Thursday at 8 p.m. and will be broadcast on PBS stations statewide.Heller was appointed last year by Gov. Brian Sandoval to fill the vacancy left when John Ensign resigned.Berkley is a seven-term congresswoman from Las Vegas.She is under investigation by the House Ethics Committee for not disclosing her husband's ties to a Las Vegas kidney center when voting on policies that benefited her husband's medical practice.Heller's campaign has focused …