Phosphodiesterase Inhibitors3',5'-Cyclic-AMP Phosphodiesterases1-Methyl-3-isobutylxanthineRolipramPhosphoric Diester HydrolasesCyclic Nucleotide Phosphodiesterases, Type 4Purinones4-(3-Butoxy-4-methoxybenzyl)-2-imidazolidinone3',5'-Cyclic-GMP PhosphodiesterasesCyclic AMPCyclic Nucleotide Phosphodiesterases, Type 3Phosphodiesterase 3 InhibitorsTheophyllineCyclic GMPPhosphodiesterase 4 InhibitorsMilrinonePhosphodiesterase 5 InhibitorsCyclic Nucleotide Phosphodiesterases, Type 5PapaverinePyrrolidinonesPhosphodiesterase I2',3'-Cyclic-Nucleotide PhosphodiesterasesCyclic Nucleotide Phosphodiesterases, Type 1ColforsinPentoxifyllineSulfonesBucladesineXanthinesNucleotides, Cyclic8-Bromo Cyclic Adenosine MonophosphatePyridazinesPurinesAdenylate CyclaseCyclic Nucleotide Phosphodiesterases, Type 6IsoproterenolVinca AlkaloidsEnoximoneCyclic Nucleotide Phosphodiesterases, Type 7Cyclic AMP-Dependent Protein KinasesAmrinoneAminophyllineBufo bufoDose-Response Relationship, DrugPhotoreceptor CellsKineticsCyclic Nucleotide Phosphodiesterases, Type 2PiperazinesDibutyryl Cyclic GMPCalciumGuanylate CyclaseErectile DysfunctionDipyridamoleAlprostadilPyridonesThionucleotidesPhthalazinesEnzyme ActivationCyclic GMP-Dependent Protein KinasesAdenosinePhenylisopropyladenosineGuinea PigsCells, CulturedTransducinPenile ErectionSecond Messenger SystemsIsoenzymesIsoquinolinesProstaglandins IStimulation, ChemicalNitric OxideCattleRod Cell Outer SegmentVasodilator AgentsProstaglandins E, SyntheticNitroprussideImidazolesTetrazolesRats, Inbred StrainsTriazinesCholera ToxinIloprostNicotinic AcidsReceptors, Adrenergic, betaOxadiazolesAdrenergic beta-AgonistsEnzyme InhibitorsSignal TransductionRats, WistarMuscle, SmoothAtrial Natriuretic FactorCardiotonic AgentsRats, Sprague-DawleyCaffeinePropranololDrug SynergismTime FactorsPyridinesMyocardiumNaphthyridinesProstaglandins E