Effects of adenosine on the development of tolerance to and physical dependence on morphine in mice

This study was performed to investigate the effects of adenosine on the development of tolerance to and physical dependence on morphine. Repeated adminstration of morphine developed tolerance and physical dependence. Adenosine (1, 2 and 4 mg $kg^{-1}$ i.p.) was administered intraperitoneally to mice for 7 days once a day 30 minutes prior to the morphine (10 mg $kg^{-1}$ s.c.). (omitted)