The study was important because it came five years before the surgeon general determined that nicotine was addictive, Waxman said.

The study showed that once rats were given a dose of nicotine, they would keep coming back for more - pushing a lever five or six times to get each dose. The researcher, Victor DeNoble, said in a letter to a journal editor that Philip Morris had blocked the study's publication.

The tobacco industry contends that nicotine is not addictive. In a statement yesterday, Philip Morris said DeNoble had concluded that nicotine did not meet the accepted criteria for drug dependence and that use of nicotine should not be considered an "addiction."

Waxman said he had sent letters to top officials and researchers for seven tobacco companies, asking them to appear on April 14 before his Energy and Commerce health and environment subcommittee.
