Caffeine Consumption and Changes in the Function of Dopaminergic Transmission: Evidence of a Hyperdopaminergic State in Rats Subchronically Treated with Caffeine

The existence of extensive interactions between the psychostimulant caffeine and the dopaminergic transmission has been clearly demonstrated by means of both neurochemical and behavioral experiments. In light of the fact that caffeine is widely consumed and considering the major role played by dopamine in mediating important physiological functions, such as movement, learning and emotional control, elucidating the features of such an interaction appears as an issue of great interest. This chapter summarizes evidence previously obtained in a rat model of subchronic caffeine administration demonstrating the capability of caffeine in triggering a hyperfunctional state involving the dopaminergic transmission in the corpus striatum which is manifested at both the behavioral and the neurochemical level. In particular, subchronic caffeine administration was found to promote the development of both sensitization to the motor stimulant effects of caffeine itself and cross-sensitization to those of amphetamine. Next to this, different neuroadaptive phenomena, which involve persistent changes in receptors' density and affinity state as well as enduring modifications in immediate early gene expression, but not dopamine release, were observed in striatal regions of rats sensitized to caffeine. The relevance of these findings to the possible mechanisms underlying caffeine-dopamine interactions is discussed