Effects of Various Selective Phosphodiesterase Inhibitors on Relaxation and Cyclic Nucleotide Contents in Porcine Iris Sphincter

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The effects of various selective phosphodiesterase (PDE) inhibitors on muscle contractility and cyclic nucleotide contents in porcine iris sphincter were investigated. Forskolin and sodium nitroprusside inhibited carbachol (CCh)-induced contraction in a concentration-dependent manner. Various selective PDE inhibitors, vinpocetine (type 1), erythro -9-(2-hydroxy-3-nonyl)adenine (EHNA, type 2), milrinone (type 3), Ro20-1724 (type 4) and zaprinast (type 5), also inhibited CCh-induced contraction in a concentration-dependent manner. The rank order of potency of IC50 was zaprinast > Ro20-1724 > EHNA ≥ milrinone > vinpocetine. In the presence of CCh (0.3 μM), vinpocetine, milrinone and Ro20-1724 increased cAMP, but not cGMP, contents. In contrast, zaprinast and EHNA both increased cGMP, but not cAMP, contents. This indicates that vinpocetine-, milrinone- and Ro20-1724-induced relaxation is correlated with cAMP, while EHNA- and zaprinast- induced relaxation is correlated with cGMP in porcine iris sphincter.
社団法人　日本獣医学会の論文