Buprenorphine‐cocaine Interactions in Mice: Effect on Locomotor Activity and Hole‐dipping Behaviour

Abstract

Abstract— The effect of cocaine and the mixed μ‐opioid partial agonist/κ‐antagonist buprenorphine on locomotor activity and hole‐dipping behaviour was investigated in mice. The drugs were given alone and in combination. Cocaine (7·5, 15, 30 mg kg−1, i.p.) significantly increased locomotion in a dose‐related manner in the hour following injection. The two 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 kg−1, i.p.; 5 min pretreatment). However, hole‐dipping was almost completely abolished in animals given combinations of cocaine and buprenorphine (0·05–5 mg kg−1, i.p.), although neither drug decreased hole‐dipping when given alone. This observation, which was not simply due to the emergence of stereotyped behaviour, suggests an interaction between buprenorphine and cocaine. 1993 Royal Pharmaceutical Society of Great Britain