reductions in time to 90 % of peak height , 90 % of relaxation time , and duration of contraction caused by peak height-augmenting concentrations of isoproterenol , epinephrine , dibutyryl cyclic amp , and 1-methyl-3-isobutylxanthine , but not of theophylline , correlated with rises in cellular cyclic amp levels .
C0000096
1-methyl-3-isobutylxanthine
C0039771
theophylline