BUPRENORPHINE COCAINE INTERACTIONS IN MICE - EFFECT ON LOCOMOTOR-ACTIVITY AND HOLE-DIPPING BEHAVIOR

The effect of cocaine and the mixed mu-opioid partial agoniSt/kappa-an tagonist buprenorphine on locomotor activity and hole-dipping behaviou r was investigated in mice. The drugs were given alone and in combinat ion. Cocaine (7.5, 15, 30 mg kg-1, i.p.) significantly increased locom otion in a dose-related manner in the hour following injection. The tw o highest doses also increased hole-dipping although this response was not consistently seen. Buprenorphine (0.5, 5 mg kg-1, i.p.) produced an increase in locomotion which occurred 30-60 min after injection but did not alter hole-dipping behaviour. A lower dose (0.05 mg kg-1) had no effect on either parameter. The locomotion induced by cocaine (15 mg kg-1, i.p.) was not modified by buprenorphine (0.05, 0.5, 1, 5 mg k g-1, i.p.; 5 min pretreatment). However, hole-dipping was almost compl etely abolished in animals given combinations of cocaine and buprenorp hine (0-05-5 mg kg-1, i.p.), although neither drug decreased hole-dipp ing when given alone. This observation, which was not simply due to th e emergence of stereotyped behaviour, suggests an interaction between buprenorphine and cocaine.