Scopolamine enhances expression of an amphetamine-conditioned place preference

Animals in the present investigation were trained for conditioned place preference by pairing the non-preferred compartment of a two chamber apparatus with either 1.5 mg kg-1 D-amphetamine or 0.05 mg kg-1 scopolamine. Some of the amphetamine-conditioned rats were injected with 0.05 mg kg-1 scopolamine as an acute treatment on the test day which followed conditioning. Although the scopolamine by itself did not induce either a preference or an aversion to the drug-paired side, it enhanced the expression of place preference in animals conditioned with amphetamine. Potentiation of this conditioned response (CR) was observed in the absence of changes in locomotor activation which would implicate general arousal as a potential mechanism. Hypotheses regarding anticholinergic mediation of CR expression via central reward mechanisms, memory retrieval, cue function and stimulus saliency are discussed, and possible neurosubstrates considered.