Relationship between Adenosine Deaminase Activity in the Cerebral Cortex and the Stimulating Effect of Caffeine in Adult Wistar Rats of Different Ages

The aim of this study was to test the hypothesis that the higher the activity of adenosinedeaminase (ADA) in the brain, the greater should be the motor activity of animals, and possibly the stronger the psychostimulant effect of caffeine. We studied the effect of caffeine (10 and 20 mg/kg) on the motor activity and ADA activity in the frontal cortex of the brain in 2- and 5-month-old rats with different levels of spontaneous motor activity. Total motor activity significantly decreased with age, which was accompanied by a decrease in ADA activity. Administration of caffeine in a dose of 10 mg/kg stimulated motor activity in both 2- and 5-month-old animals, while ADA activity decreased in 2-month-old rats and increased in 5-month-old animals. Administration of caffeine in a dose of 20 mg/kg did not change the motor activity, however, in 5-month-old animals it led to an even greater increase in ADA activity. Thus, the age-related decrease in motor activity can be due to a decrease in ADA activity. However, the effect of caffeine on motor activity is not directly related to ADA activity in the cerebral cortex.