Figure 5.

(A) Effects of tetrodotoxin (TTX) and atropine, alone or in combination, on the contractile responses evoked by protease activated receptor 4 (PAR₄) activating peptide, AYPGKF-NH₂, on the longitudinal muscle of rat colon. The contractile responses to AYPGKF-NH₂ were significantly reduced by TTX (1 μM) or atropine (1 μM). The combination of atropine (1 μM) and TTX (1 μM) did not cause any further reduction. (B) Effects of SR140333 and SR48968, alone, in combination, or after treatment with TTX, on the contractile responses evoked by PAR₄ activating peptide, AYPGKF-NH₂, on the longitudinal muscle of rat colon. The contractile responses to AYPGKF-NH₂ were significantly reduced by SR140333 (1 μM), an antagonist of NK₁ receptors, by SR48968 (1 μM), an antagonist of NK₂ receptors, and even more by a combination of SR48968 (1 μM) and SR140333 (1 μM). AYPGKF-NH₂ did not induce any response in the presence of a combination of SR48968 (1 μM), SR140333 (1 μM), and TTX (1 μM). The contractile effects are expressed as a percentage of the contraction to carbachol (CCh 10 μM). Each value is mean (SEM) of five experiments. *p<0.05 compared with control value; †p>0.05 compared with TTX or atropine alone; ‡p<0.05 compared with SR140333 and SR48968 alone; §p<0.05 compared with the combination of SR140333 and SR48968.