The Relationship Between Visceral Hyperalgesia And The Expression Of CGRP In Colon And Central Nervous System In Developing Rat

Objective:Establish the model of visceral hyperalgesia in developing rats. Detecting the distribution and expression in colon, dorsal horn of lumbosacral spinal cord and different brain regions(hypothalamus paraventricular nucleus, nucleus raphe magnus and anterior cingulated cortex) of developing rats with visceral hyperalgesia, in order to study the role of abnormal expression of CGRP in brain-gut axis in forming the visceral hyperalgesia. This study can deeply understanding the pathophysiological mechanism of the abdominal pain related to functional gastrointestinal disease in children and provide the theoretical basis for taking the available measures and the development of therapeutic drugs in clinic.Method:According to the factorial design, 32 SD rats were divided into four groups with each 8: Group A1B1 impose on CI at neonatal period and imposed on Colorectal Distension (CRD) at 6-week age; Group A1B2:impose on CI at neonatal period and not imposed on CRD at 6-week age; Group A2B1:not impose on CI at neonatal period and imposed on CRD at 6-week age; Group A2B2: not impose on CI at neonatal period and not imposed on CRD at 6-week age. Group A1B1 and Group A1B2 were treated with colorectal irritation once a day during 7 consecutive days from the 8th day after birth, Group A2B1 and Group A2B2 were just seperated from mother,but not imposed on CI. Then, conventionally breeding till the young period (6-week age), the following study was implemented:①By the method of Abdonminal Withdrawal Reflex (AWR),Pain Thresholds and electrophysiological on external oblique to evaluate visceral algesthesia of intestinal tract.②Sampled the colon, L6～S2 of spinal cord and different brain regions(hypothalamus paraventricular nucleus, raphe magnus and anterior cingulated cortex), the semi-quantity analysis of staining density and the cell numbers of CGRP-Like Immunoreactivity of these sites were made through immunohisrochemical coloration and computer image analyzing system.③Select descending colon to do patho- ligical examination.α=0.05 was considered significant.Result:[1]At the 6-week age, The AWR scores and the amplitudes of spike EOMA increased gradually with the rising of the CRD pressure in developing rats; When the CRD pressure were 20mmHg, 40mmHg, 60mmHg, the AWR score was higher in the Group A1B1 than Group A2B1 signigficantly. When pressure reached 80mmHg,there was no significant difference of AWR scores between two gruops. When the CRD pressure were 15mmHg, 30mmHg and 45mmHg, the spikes were higher in the Group A1B1 than Group A2B1 signigficantly. When pressure were 60mmHg,80mmHg, the differences were no statistical significance. The Pain Thresholds of Group A1B1 and Group A2B1 were 14.79±3.14mmHg, 37.71±5.3mmHg respectively (F=109.4,P<0.01). There were no obvious histopatholigical changes in descending colon in all rats. [2]Rats accepted CI in neonatal period and noxious stimulation of CRD could make the number of CGRP-Like Immunoreactivity increasely and staining density of CGRP-Like Immunoreactivity decrease significantly in the colon,the dorsal horn of spinal cord and different brain regions such as hypothalamus paraventricular nucleus,nucleus raphe magnus and anterior cingulated cortex and so on.Conclusion: The persistent CI in neonatal period can result in low pain threshold and chronic high visceral pain sensibility in developing rats; There is no histological change found in colorectal tissues; Rats with abnormal chronic visceral pain may involve in the brain-gut axis. No matter in colon,or in the dorsal horn of spinal cord and different brain regions such as hypothalamus paraventricular nucleus,nucleus raphe magnus and anterior cingulated cortex and so on, CGRP are all involved in the changeing of visceral pain sensitivity; The persistent CI in neonatal period can cause nervous system abnormalities and sensitization. CGRP as a neurotransmitter,may involved in the changing of the pathophysiological.