Chronic caffeine exposure potentiates nicotine self administration in rats

The prevalence of tobacco smoking and coffee drinking place nicotine and ca ffeine among the most used licit drugs in many societies and their consumpt ion is often characterised by concurrent use. The pharmacological basis for any putative interaction between these drugs remains unclear. Epidemiologi cal reports support anecdotal evidence, which suggests that smokers consume caffeine to enhance the euphoric effects of nicotine. The aim of the prese nt experiment was to examine effects of chronic exposure to caffeine on res ponding maintained by nicotine. Sprague-Dawley rats consuming caffeine (app roximately 150-180 mg/kg per day) in their drinking water for 7 days prior to the beginning and throughout behavioural testing acquired intravenous ni cotine self-administration (0.03 mg/kg per infusion) more rapidly than did controls. In a cross-over design, exclusion of caffeine brought levels of n icotine self-administration back to baseline, while adding caffeine to the drinking water of control rats increased responding maintained by nicotine over 90%. These findings strongly suggest that caffeine can potentiate the reinforcing properties of nicotine, thus highlighting the importance of env ironmental factors in shaping and maintaining tobacco smoking.