Caffeine potentiates the discriminative-stimulus effects of nicotine in rats.
RATIONALE: Caffeine and nicotine are the main psychoactive ingredients of coffee and tobacco, respectively, with a high frequency of concurrent use in humans. OBJECTIVES: The aim of the present study was to examine the interaction of caffeine and nicotine in rats trained to discriminate nicotine from saline. METHODS: Two groups of male Sprague-Dawley rats ( n=8 per group) were trained to discriminate 0.4 mg/kg nicotine, SC, from saline under a fixed ratio schedule of food presentation. One group of rats was chronically exposed to caffeine (1.0 mg/ml) dissolved in their drinking water whereas the other group was exposed to tap water. Effects of IP injections of caffeine on nicotine-lever selection were subsequently examined. In separate groups of rats exposed to the same caffeine-drinking or water-drinking regimen, effects of caffeine pretreatment on nicotine plasma levels were evaluated. RESULTS: Although caffeine (1.0-30.0 mg/kg) did not generalize to nicotine when administered alone, it markedly potentiated discriminative-stimulus effects of the threshold dose of nicotine (0.05 mg/kg) in both water- and caffeine-drinking rats. Nicotine plasma levels were, however, not affected by acute or chronic caffeine exposure. CONCLUSIONS: Caffeine appears to enhance the discriminative-stimulus effects of the threshold dose of nicotine by a pharmacodynamic rather than a pharmacokinetic interaction. This suggests that caffeine consumption may be a contributing factor in the onset, maintenance of and relapse to tobacco dependence.[1]References
- Caffeine potentiates the discriminative-stimulus effects of nicotine in rats. Gasior, M., Jaszyna, M., Munzar, P., Witkin, J.M., Goldberg, S.R. Psychopharmacology (Berl.) (2002) [Pubmed]
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