after 10 days of oral administration of caffeine ( 1 g/l , in drinking water ) to six rats , the mean ( +/- sem ) concentrations of caffeine in plasma , brain , and kidney were 18.6 +/- 6.0 micrograms/ml , 16.2 +/- 1.5 micrograms/g , and 18.9 +/- 2.0 micrograms/g , respectively .
C0086045
concentrations
C0006104
brain