胃扩张刺激对大鼠大脑皮层及海马CCK mRNA表达的影响

CHANGES IN THE mRNA CONCENTRATION OF PREPROCHOLECYSTOKININ IN RAT CEREBRAL CORTEX AND HIPPOCAMPUS AFTER GASTRIC DISTENSION

胆囊收缩素（chalecystokinin，CCK）是脑肠肽中的一种，被认为是他因子。本实验采用以地高辛标记的CCK。DNA为探针的原位杂交和半定量RTPCR技术，用水囊扩张胃作为对胃壁的机械刺激模拟食物对胃的充盈作用，观察大鼠大脑皮层和海马内含CCK神经元CCKmRNA表达的变化情况。结果表明：（1）对照组大鼠大脑皮层和海马CA3等区有散在CCKmRNA表达阳性细胞；（2）胃扩张刺激后，皮层和海马等区内CCKmRN表达信号明显增强，表现为CCKmRN阳性神经元体积增大，数量增加，细胞内酶反应产物密集，积分光密度显著增加（P＜0．01）；（3）半定量RTPCR检测结果显示：实验组大鼠大脑皮层、海马标本电泳图有明显的158hp扩增条带，信号比对照组明显增强。实验组大鼠大脑皮层、海马CCKmRN相对含量显著增加（P＜0．01）。可见，在胃扩张机械性刺激作用下，皮层、海马CCK神经元内CCKmRNA表达增强，来自胃扩张刺激引起的神经信号可传入到中枢神经系统高级部位的皮层、海马等区，使脑细胞核内CCK基因转录水平发生变化。结果提示，中枢神经系统高级部位CCK的生物合成过程参与中枢对胃内压和胃运动的调控。

Cholecyctokinin-octapeptide (CCK-8) is one of the brain-gut peptides widelydistributed in neurons of the central nervous system, especially in cerebral cortex andhippocampus. This peptide is thought as a neurotransmitter or modulator. The role ofcentral CCK in the integration of gastric motility and food intake is still unclear. Thepresent investigation was undertaken to see whether the gastric distension exerts someeffect on the expression of CCK mRNA in cerebral cortex and hippocampus by means ofin situ hybridization and semi-quantative RT-PCR techniques. The results are as follows.(1) Discrete positive hybridization cells were seen in cerebral cortex and hippocampus incontrol group. (2) Significant increases of CCK mRNA expression in cerebral cortex andhippcompus produced by gastric distention observed by increased of the volume, thenumber, the IOD and the SA of positive cells. (3) Amplified bands of the expected size of 158 base pairs were found in cerebral cortex and hippocampus, and signals of gastricdistention group were higher than those of control group. The results from RT-PCR assayare in agreement with those based on in situ hybridization. These results imply thatbiosynthesis of CCK-containing neurons in cerebral cortex and hippocampus is acceleratedby afferent signals from gastrointestinal system and may be involved in regulation of gastricmotility and food intake.