Involvement of nitric oxide and tachykinins in the effects induced by protease-activated receptors in rat colon longitudinal muscle

The aim of the present study was to verify a possible involvement of nitric oxide (NO) and of tachykinins in the contractile and relaxant effects caused by the activation of protease-activated receptor (PAR)-1 and PAR-2 in the longitudinal muscle of rat colon. Mechanical responses to the PAR-1 activating peptides, SFLLRN-NH2 (10 nM–10 μM) and TFLLR-NH2 (10 nM–10 μM), and to the PAR-2-activating peptide, SLIGRL-NH2 (10 nM–10 μM), were examined in vitro in the absence and in the presence of different antagonists. The relaxation induced by SFLLRN-NH2, TFLLR-NH2 and SLIGRL-NH2 was antagonised by the inhibitor of NO synthase L-Nω-nitroarginine methyl ester (300 μM), or by the inhibitor of the gu…