Compared with their BALB/cBy controls, SCID mice have a significantly greater abdominal response to colorectal distension (CRD) at the distension levels of 0.04 to 0.1 mL increasing the intensity of EMG response by 384% to 132%, respectively (P<0.01; P<0.01; P<0.01; P<0.001). PAR-4 activation effectively reverses this hypersensitivity (P<0.01, P<0.05; P<0.05; P<0.05) .