TheophyllinePhosphodiesterase Inhibitors1-Methyl-3-isobutylxanthine3',5'-Cyclic-AMP PhosphodiesterasesRolipramPhosphoric Diester HydrolasesPurinones4-(3-Butoxy-4-methoxybenzyl)-2-imidazolidinoneCyclic AMPCyclic Nucleotide Phosphodiesterases, Type 43',5'-Cyclic-GMP PhosphodiesterasesPhosphodiesterase 3 InhibitorsPhosphodiesterase 4 InhibitorsCyclic GMPMilrinoneCyclic Nucleotide Phosphodiesterases, Type 3PapaverinePhosphodiesterase 5 InhibitorsXanthinesPyrrolidinonesCyclic Nucleotide Phosphodiesterases, Type 5BucladesinePhosphodiesterase I2',3'-Cyclic-Nucleotide PhosphodiesterasesCyclic Nucleotide Phosphodiesterases, Type 1AminophyllineColforsinPentoxifyllineSulfonesNucleotides, Cyclic8-Bromo Cyclic Adenosine MonophosphatePyridazinesAdenylate CyclasePurinesIsoproterenolAdenosineEnoximoneVinca AlkaloidsDose-Response Relationship, DrugAmrinoneKineticsCyclic AMP-Dependent Protein KinasesTheobromineCalciumBufo bufoDipyridamoleCyclic Nucleotide Phosphodiesterases, Type 2Purinergic P1 Receptor AntagonistsPhenylisopropyladenosinePhotoreceptor CellsCyclic Nucleotide Phosphodiesterases, Type 6Guinea PigsCaffeineDibutyryl Cyclic GMPAlprostadilBronchodilator AgentsStimulation, ChemicalPiperazinesGuanylate CyclaseErectile DysfunctionPhthalazinesCells, CulturedPyridonesThionucleotidesVasodilator AgentsEnzyme ActivationCyclic Nucleotide Phosphodiesterases, Type 7Drug InteractionsCholera ToxinRats, Inbred StrainsDelayed-Action PreparationsProstaglandins IPenile ErectionCyclic GMP-Dependent Protein KinasesNitric OxideSecond Messenger SystemsAdrenergic beta-AgonistsIsoquinolinesImidazolesNitroprussideAdenosine-5'-(N-ethylcarboxamide)Prostaglandins E, SyntheticCattlePropranololProstaglandins ENicotinic AcidsTransducinTime FactorsTetrazolesDrug SynergismMuscle, SmoothIsoenzymesTriazinesReceptors, Adrenergic, betaReceptors, Purinergic P1NaphthyridinesRats, WistarIloprostEnzyme InhibitorsRod Cell Outer Segment