title: T-0156, a novel phosphodiesterase type 5 inhibitor, and sildenafil have different pharmacological effects on penile tumescence and electroretinogram in dogs.
abstract: T-0156 (2-(2-methylpyridin-4-yl)methyl-4-(3,4,5-trimethoxyphenyl)-8-(pyrimidin-2-yl)methoxy-1,2-dihydro-1-oxo-2,7-naphthyridine-3-carboxylic acid methyl ester hydrochloride) is a newly synthesized phosphodiesterase type 5 inhibitor, and its potency and selectivity are higher than those of sildenafil in an enzyme assay. In the present study with anesthetized dogs, we examined the effects of intravenous T-0156 or sildenafil on the pelvic nerve stimulation-induced penile tumescence and light-adapted flicker stimulation-induced electroretinogram, parameters of which are reported to be indicators for inhibition of phosphodiesterase type 5 and type 6, respectively. Both compounds potentiated the penile tumescence in a dose-dependent manner. T-0156 at 10 microg/kg and sildenafil at 100 microg/kg showed almost the same potentiating percentage (181.5+/-31.1% and 190.0+/-37.9%) in spite of the plasma concentration of T-0156 being about five times lower than that of sildenafil (16.7+/-1.6 and 78.8+/-5.3 ng/ml), indicating that the effect of T-0156 on tumescence is more potent than that of sildenafil. While the high dose of T-0156 (1000 microg/kg) reduced the amplitude and increased the latency of the electroretinogram positive wave, the effects of T-0156 were conversely weaker than those of sildenafil (reduction of amplitude; T-0156: 41.1+/-8.0%, sildenafil: 71.7+/-3.9%, increase of latency; T-0156: 3.9+/-0.6%, sildenafil: 14.5+/-1.4%, at 1000 microg/kg). These results clearly showed the difference in the properties of T-0156 and sildenafil in pharmacological studies with anesthetized dogs, and the difference appeared to correspond with their inhibitory potencies for phosphodiesterase type 5 and type 6. It was concluded that T-0156 would be a useful pharmacological tool as a potent and highly selective phosphodiesterase type 5 inhibitor.
authors.affiliation: Discovery and Pharmacology Research Laboratories, Tanabe Seiyaku Co., Ltd., 2-2-50, Kawagishi, Toda, Saitama 335-8505, Japan. mochida@tanabe.co.jp
authors.forename: Hideki
authors.initials: H
authors.lastname: Mochida
authors.forename: Tsunehisa
authors.initials: T
authors.lastname: Noto
authors.forename: Hirotaka
authors.initials: H
authors.lastname: Inoue
authors.forename: Koji
authors.initials: K
authors.lastname: Yano
authors.forename: Kohei
authors.initials: K
authors.lastname: Kikkawa
mesh_terms: D015106:3',5'-Cyclic-GMP Phosphodiesterases; D000818:Animals; D054706:Cyclic Nucleotide Phosphodiesterases, Type 5; D004285:Dogs; D004305:Dose-Response Relationship, Drug; D004596:Electroretinography / Q000379:methods; D008297:Male; D009287:Naphthyridines / Q000737:chemistry / Q000494:pharmacology*; D010410:Penile Erection / Q000187:drug effects* / Q000502:physiology; D010726:Phosphodiesterase Inhibitors / Q000494:pharmacology*; D010727:Phosphoric Diester Hydrolases / Q000378:metabolism*; D010775:Photic Stimulation / Q000379:methods; D010879:Piperazines / Q000737:chemistry / Q000494:pharmacology*; D011687:Purines; D011743:Pyrimidines / Q000737:chemistry / Q000494:pharmacology*; D012160:Retina / Q000187:drug effects* / Q000201:enzymology / Q000502:physiology; D000068677:Sildenafil Citrate; D013450:Sulfones
chemical_list: D009287:Naphthyridines; D010726:Phosphodiesterase Inhibitors; D010879:Piperazines; D011687:Purines; D011743:Pyrimidines; D013450:Sulfones; C473961:T0156; D000068677:Sildenafil Citrate; D010727:Phosphoric Diester Hydrolases; D015106:3',5'-Cyclic-GMP Phosphodiesterases; D054706:Cyclic Nucleotide Phosphodiesterases, Type 5