The Rupee slipped by eight paise to 55.21 against the US Dollar in the opening trade today due to rising demand for the greenback by importers, dealers at the Interbank Foreign Exchange said. The local unit registered intra day high and low at 55.23 and 55.18 respectively against the greenback with a minor fluctuation. The domestic unit was weak following Dollar's gain against other world currencies and weak opening in equity market also dampened the sentiment, dealers said.