Effects of chronic caffeine on brain adenosine receptors: regional and ontogenetic studies

The effect of chronic caffeine treatment on three different binding sites in five brain areas of mice is characterized. The sites studied were the adenosine receptor, using [3H] diethylphenylxanthine, the benzodiazepine receptor, using [3H] diazepam and the adenosine uptake site, using [3H] nitrobenzylthioinosine. Significant increases were only observed in adenosine receptors with the greatest degree of change seen in the cerebellum and brain stem at both 16 and 23 days of caffeine treatment. The lack of significant effects of chronic caffeine on benzodiazepine receptors and adenosine uptake sites indicates that the caffeine effect is specific. The effect of chronic caffeine treatment on the ontogeny of adenosine receptors was also studied with the result showing a significantly accelerated development of the receptor in the caffeine treated animals. The adult adenosine receptor levels were 20-30% higher than those observed in control animals. The observed alterations in adenosine receptor number which occur as a consequence of caffeine consumption may underlie some of the behavioral effects of this cortical stimulant as well as provide insights concerning the mechanisms of tolerance to and dependence on caffeine.