Persistance of visceral hypersensitivity in the rat models induced by rectal distention combined with limb constraint

Objective To assess the persistence of visceral hypersensitivity in rat models induced by rectal distension combined with limb constraint.Methods Thirty-two 8-week old Sprague-Dawley(SD) rats were randomly divided into control group(n=16) and model group(n=16).Rectal distension with limb constraint lasting for 2 weeks was operated on the model group rats.Visceral sensitivity was evaluated by abdominal withdrawal reflex(AWR).Based on the AWR scores,the rats in the control group were randomly divided into group A(n=8) and group B(n=8),and the model group was randomly divided into group C(n=8) and group D(n=8).Colon specimens of the groups A and C were taken under anesthesia.Group B and group D received normal breeding until 18-weeks old,and then group D received the same stimulation.AWR scores and colon specimens were obtained in the same way.The ultrastructure of mast cells was observed by electron microscopy.Toluidine blue staining was performed to count mast cells(MC).Proteaseactivated receptor 2(PAR2) was analyzed by Western blot.Results AWR score of the group C was significantly higher than that of group A,and that of the group D was lower than that of the group C(P0.01).Intestinal MC count of the group C was significantly higher than that in the group A,and that of the group D was significantly lower than that of the group C(P0.01).Mast cell degranulation was visible in the group C,neither in other groups.PAR2 expression level of the group C was significantly higher than that of the group A,and that of the group D was significantly lower than that of the group C(P0.01).Conclusion The sensitivity of visceral hypersensitivity in the rat models induced by rectal distension combined with limb constraint is attenuated along with the increase of age in weeks.