A, standard preparation. B, intact preparation. C, longitudinal smooth muscle preparation with attached circular muscle only. D, isolated longitudinal smooth muscle preparation. In each preparation, SNP produced a similar contraction, which was unaffected by pre-application of TTX, but significantly inhibited by ODQ. However, 8-bromo-cGMP (1 mm) mimicked the SNP-induced contraction. These data indicate that SNP has a direct excitatory effect on oesophageal longitudinal smooth muscle via a cGMP-dependent signalling pathway. n = 5, *P < 0.05.