·To observe the effect of protease activated receptor 2 (PAR2) on colonic motility in chronic stress-treated mice, and investigate its mechanism.

·The mice were treated with chronic heterogenous stress for 14 days to establish the chronic stress model. Western blotting was used to determine the expressions of PAR2, platelet-derived growth factor receptor α (PDGFRα) and small conductance calcium-activated potassium channel 3 (SK3 channel), while the effects of PAR2 agonist and SK3 channel antagonist on colonic motility were observed by isometric tension experiment. T-test was used for statistical analysis. Statistical significance was accepted at the value of P<0.05.

·Twenty-four hours after being treated by stress stimulation, the mice demonstrated a decrease of colonic transmission because the number of fecal pellets decreased significantly; simultaneously, the expression of PAR2 increased in the colon smooth muscle tissue of chronic stress-treated mice. The inhibition of colonic smooth muscle contractions by PAR2 agonist was more significant in the chronic stress-treated mice than that in the control ones. The expression of PDGFRα in colonic smooth muscle tissue of chronic stress-treated mice increased, but the expression of SK3 had no obvious change, compared with the control mice. The inhibition of colonic smooth muscle contractions by SK3 channel antagonist was not significantly different between chronic stress-treated mice and the control mice.

·In the colons of chronic stress-treated mice, PAR2 activity and expression both increase, which may be responsible for the decrease of colonic motility.