Caffeine and the dopaminergic system

Caffeine is the most widely consumed psychostimulant substance, being self-administered throughout a wide range of conditions and present in numerous dietary products. Due to its widespread use and low abuse potential, caffeine is considered an atypical drug of abuse. The main mechanism of action of caffeine occurs via the blockade of adenosine A(1) and A(2A) receptors. Adenosine is a modulator of CNS neurotransmission and its modulation of dopamine transmission through A(2A) receptors has been implicated in the effects of caffeine. This review provides an updated summary of the results reported in the literature concerning the behavioural pharmacology of caffeine and the neurochemical mechanisms underlying the psychostimulant effects elicited by caffeine. The review focuses on the effects of caffeine mediated by adenosine A(2A) receptors and on the influence that pre-exposure to caffeine may exert on the effects of classical drugs of abuse.