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Caffeine exposure sensitizes rats to the reinforcing effects of cocaine
B A Horger1, P J Wellman, A Morien
1Department of Psychology, Texas A & M University, College Station 77843.
Abstract:
The present study examined the effect of pre-exposure to a moderate dose of caffeine (20 mg kg-1) on the acquisition of self-administration of cocaine (0.125 mg kg-1/infusion or 0.25 mg kg-1/infusion) in the rat. Rats pre-exposed to caffeine acquired self-administration more rapidly. Furthermore, sensitization to cocaine's reinforcing effects was accompanied by an increase in the neurochemical response of the mesolimbic dopamine system to an acute injection of cocaine (10 mg kg-1, i.p.) as measured by in vivo microdialysis. Thus, the data suggest that exposure to caffeine can increase the reinforcing effects of cocaine, possibly via an enhanced response to the mesolimbic dopamine system.