ABSTRACT
Genetic variations in the encoding of the adenosine receptors exist, and these are related to habitual caffeine consumption and the behavioural effects of caffeine. This chapter focuses on the central nervous system (CNS) and the behavioural effects associated with this. It suggests that caffeine shares four behavioural pharmacological effects with classic drugs of abuse/dependence: reinforcing effects, discriminative/subjective effects, tolerance and physical dependence. The effects of caffeine during sleep loss have been examined over a dose range from 75 to 1200 mg per 24 hours. Fatigue is a major cause of road traffic accidents, and the fact that caffeine can reduce the effects of sleepiness has meant that this has been examined using simulated driving. A single-photon emission computed tomography (SPECT) assessment of brain activation in humans showed that caffeine activates regions involved in the control of vigilance, anxiety and cardiovascular regulation but did not affect areas involved in reinforcement and reward.
