the duration of constriction was reduced after pretreatment by theophylline , 3-isobutyl-1-methyl-xanthine , bromo-camp , or bromo-cgmp , suggesting that the relaxation was related to an increase in cyclic nucleotide levels in the cell .
C0039771
theophylline
C0000096
3-isobutyl-1-methyl-xanthine