Establishment of model of visceral pain due to colorectal distension and its behavioral assessment in rats

Figure 1 AWR scores under stepping increased pressure of colorectal distension ^aP < 0. 05 , ^bP < 0.01 vs the basal pressure.

Figure 2 Repeated observations of pain thresholds after CRD at different times. The threshold was higher at the first distention, and then declined. It became stable after 3 trials. The mean pain threshold was 3.69 ± 0.35 kPa.

Figure 3 Effect of morphine on AWR to CRD. The pain thresholds of the rats that received 2 mg/kg, 4 mg/kg, 8 mg/kg of morphine respectively were significantly higher than the basal values (P < 0.01). ^bP < 0.01 vs the basal values.