the addition of 8-bromo cyclic amp , forskolin , theophylline , and 3-isobutyl-1-methylxanthine to the medium of pc 12 cells resulted in an increase in gtp cyclohydrolase i activity , but had no effect on dihydropteridine reductase activity , except theophylline which caused a decrease in dihydropteridine reductase activity at 96 h .
C0000096
3-isobutyl-1-methylxanthine
C0039771
theophylline