Smooth Muscles

Results. In general, CNP and SNP exerted differential inhibitoiy effects on muscarinic-receptorinduced responses in CM and Sph isolated from the various species. Thus in bovine CM, SNP stimulated cGMP formation in a timeand concenu^ation-dependent manner and dose dependently inhibited CCh-induced IP3 production and contraction. These effects were inhibited by LY 83583, a soluble guanylyl cyclase inhibitor, and mimicked by 8-Br-cGMP, a cell-membrane permeable analogue of cGMP. The inhibitoiy effects of the soluble cGMP analogue are tissue and species specific. Sodium nitroprusside had no effect on the muscarinic responses in bovine Sph, but it attenuated CCh-induced contractions in Sph isolated from cats, dogs, and rabbits. In bovine Sph, CNP increased cGMP accumulation in a timeand dose-dependent manner and dose dependently inhibited CCh-induced IP3 production and contraction. LY 83583 had no effect on the muscarinic responses. Gtype natriuretic peptide attenuated CCh-induced contraction in CM isolated from monkey and human, but it had no influence on this response in CM isolated from cows, cats, and dogs.