THE RELATIONSHIP BETWEEN THE EXPRESSION OF CGRP IN COLON AND VISCERAL HYPERALGESIA IN YOUNG RATS

Objective: Colorectal irritation(CI) was used to establish the model of visceral hyperalgesia in young rats.in order to explore the relationship between the expression of calcitonin gene-related peptide(CGRP) in colon and the visceral hyperalgesia.Methods: Eight day old Sprague-Dawley rats were divided into 4 groups(n=8).Group A were imposed with CI at neonatal period and with colorectal distension(CRD) at 6-week age;Group B were imposed with CI at neonatal period but not CRD at 6-week age;Group C were not imposed with CI at neonatal period but with CRD at 6-week age;Group D were imposed with neither CI nor CRD at 6-week.Group A and Group B were treated with colorectal irritation once a day for 7 consecutive days from the 8th day after birth.Conventionally breeding till 6-week age,the visceral sensitivity of Group A and Group C was evaluated.Then,using SABC immunohistochemical assay to detect the expression of CGRP in colon of all rats in 4 groups.Results: The abdominal with drawal reflex(AWR) scores increased gradually with the rising of the CRD pressure.At the same pressure,the AWR score were signigficantly higher in the Group A than Group C(F=85.172,P0.001).The pain thresholds of Group A and Group C were 14.79±3.14mmHg and 37.71± 5.3mmHg respectively(F=109.4,P0.01).Conclusion: The Persistent CI in neonates can result in visceral hyperalgesia in young rats.The increased expresson of CGRP in colon may account for this change.