幼鼠内脏痛高敏感性与不同脑区降钙素基因相关肽表达的关系

Relationship between Visceral Hyperalgesia in Developing Rats and Expression of Calcitonin Gene-Related Peptide in Different Regions of Brain

目的采用新生期伤害性结直肠刺激（CI）建立幼鼠痛高敏感模型,检测痛觉敏感幼鼠模型下丘脑室旁核、中缝核和前皮质扣带回内降钙素基因相关肽（CGRP）的分布和表达,探讨不同脑区CGRP异常表达参与痛觉高敏感形成的可能机制。方法 8日龄新生SD大鼠分为4组,每组8只。CI＋CRD组新生期给予CI,并在6周龄时给予结直肠扩张（CRD）刺激;CI组新生期给予CI,但在6周龄时不予CRD刺激;CRD组新生期不予CI,6周龄时给予CRD刺激;对照组新生期不予CI,6周龄时也未给予CRD刺激。CI＋CRD组和CI组乳鼠在出生8-15 d,每天接受1次CI。常规喂养至6周龄,CI＋CRD组和CRD组幼鼠进行CRD刺激下内脏痛敏感性评价。采用SABC免疫组织化学法检测4组幼鼠不同脑区内CGRP表达情况。结果随着CRD的增加,CI＋CRD组和CRD组幼鼠腹外斜肌放电波幅逐渐增加。在CRD为2 kPa、4 kPa、6 kPa和8 kPa扩张压刺激下,CI＋CRD组腹外斜肌放电幅值显著高于CRD组,差异有统计学意义（F=43.261,P=0.000;F=15.389,P=0.002;F=8.024,P=0.013;F=6.287,P=0.025）。而当CRD为10 kPa高扩张压刺激时,CI＋CRD组和CRD组腹外斜肌放电幅值差异无统计学意义（F=0.502,P=0.490）。新生期CI导致幼鼠下丘脑室旁核、前扣带回皮质、中缝核内CGRP阳性细胞数明显增加的主效应分别为12.23、12.74和11.81,接受CRD刺激后可导致幼鼠CGRP阳性细胞数明显增加的主效应分别为16.81、18.00和17.18。结论新生期持续CI会造成幼鼠痛阈下降,出现慢性内脏痛高敏感性。幼鼠慢性内脏痛敏感性异常可能与前皮质扣带回、下丘脑室旁核、中缝核内CGRP异常表达相关。CGRP可能作为一种神经递质参与内脏痛觉敏感的改变。

Objective To establish the model of visceral hyperalgesia in developing rats by colorectal irritation（CI）,detect the distribution and expression of calcitonin gene-related peptide（CGRP） in hypothalamus paraventricular nucleus,nucleus raphe magnus and anterior cingulated cortex of developion rats,explore the role of abnormal expression of CGRP in forming the visceral hyperalgesia.Methods Eight-day-old Sprague-Dawley rats were divided into 4 groups（n=8）：CI＋colorectal distension（CRD） group imposed on CI at neonatal period and imposed on CRD at 6-week age;CI group：imposed on CI at neonatal period and not imposed on CRD at 6-week age;CRD group：not imposed on CI at neonatal period and imposed on CRD at 6-week age;Control group：not imposed on CI at neonatal period and not imposed on CRD at 6-week age.CI＋CRD group and CI group were treated with CI once a day during 7 consecutive days from the 8th day after birth.Conventionally breeding till the young period（6-week age）,the visceral sensitivity in CI＋CRD group and CRD group was evaluated.Then,strept actividin biotin complex（SABC） immuno-histochemical assay was used to detect the expression of CGRP in different brain regions of all rats in the 4 groups.Results The amplitudes of spike external oblique muscle of abdomen increased gradually with the rising of the CRD pressure in developing rats.When the CRD pressure were 2 kPa,4 kPa,6 kPa and 8 kPa,the spikes were signigficantly higher in the CI＋CRD group than those in CRD group（F=43.261,P=0.000;F=15.389,P=0.002;F=8.024,P=0.013;F=6.287,P=0.025）.When pressure were 10 kPa,the difference was no statistical significance between the 2 groups（F=0.502,P=0.490）.Rats accepted CI in neonatal period could make the number of CGRP-like immunoreactivity increasely in hypothalamus paraventricular nucleus,nucleus raphe magnus and anterior cingulated cortex of developing rat,main effects were 12.23,12.74 and 11.81,respectively.Rats accepted CRD could make the number of CGRP-like immunoreactivity increasely in hypothalamus paraventricular nucleus,nucleus raphe magnus and anterior cingulated cortex of developing rat,main effects were 16.81,18.00 and 17.18,respectively.Conclusions The persistent CI in neonatal period can result in low pain threshold and chronic high visceral pain sensibility in developing rats.The abnormal expression of CGRP in hypothalamus paraventricular nucleus,nucleus raphe magnus and anterior cingulated cortex may be involved in abnormal chronic visceral pain.CGRP as a neurotransmitter,may be involved in the change of visceral pain sensitivity.