treatment of toad rods with phosphodiesterase inhibitors ( 3-isobutyl-1-methylxanthine , caffeine , theophylline , papaverine , and ro 20-1724 ) modifies the properties of the intracellular voltage responses to dim flashes of light .
C0000096
3-isobutyl-1-methylxanthine
C0039771
theophylline