| [Background and Aims] The irritable bowel syndrome(IBS) is a common disorder in gastroenterology, but the pathophysiology of IBS is still unclear. In recent years, experiments have revealed that the concentrations of some kinds of brain-gut peptides/gut hormones were abnormal in the plasma and/or the intestinal mucosa of IBS patients. Furthermore, some authors reported that the mast cells in the ileocecal junction were abnormal. Through PET and fMRI examinations, it was found that the functional status of some nerve centers in the brains of IBS patients was different from that of the normal subjects. The above results indicate that there may be disturbance in the nerve system, the endocrine system and the immune system in IBS patients. However, it is almost impossible to conduct further experiments in the enteric nervous system and the central nervous system(CNS) in IBS patients. One year ago, our working group set up a new concept rat model of constipation- predominant IBS (C-IBS), which may be useful in doing such experiments. Substance P (SP), vasoactive intestinal peptide (VIP), gamma-aminobutyric acid (GABA), acetylcholine(Ach)and norepinephrine (NE)are important neuretransmitters in the bowel and the CNS, but there are few investigations on their roles in the muscular layer of the bowel and the CNS in IBS. In this dissertation, the aim is to investigate the expressions of these neurotransmitters in the bowel and the CNS of the rat model of C-IBS and to explore their possible roles in the pathogenesis of IBS.[Materials and Methods] The tissue samples were obtained from the rats of control group and the rat model of C-IBS, which was set up and reported by our group. 20 Wistar rats of postnatal 4 weeks were divided into two groups randomly. 10 rats of the model group - Group A was treated with stomach irritation of 2.0ml water at 0-4 C once a day for 2 weeks. After the irritation, rats were raised in the normal condition for another two weeks. The other 10 rats of Group C were regarded as the control group. The granules and moisture contents of feces after cool water irritation were significantly lower in the model group than those in the control group. After suspending stomach irritation with cool water, this tendency lasted at least for fourteen days. At the 28th day, the rats of both groups were put to death, and the specimens of the ileocecal junction, colon, spinal cord and brain were collected and stained by immunohistochemical staining using anti-SP, VIP, GABA, acetylcholinesterase (AchE)and tyrosine hydroxylase (TH) antibodies respectively. The staining results were analyzed semi-quantitatively by computerized color image analyzer using the following parameters: immunoreactive area, mean density and integrated optical density (IOD).[Results] As for ileocecal junction and colon, mean density of SP immunoreactive tissues in the model group were significantly higher than those in control group(P<0.05), meanwhile there were no differences between the two groups concerning the immunoreactive area and IOD (P> 0.05); immunoreactive area, mean density and IOD of VIP immunoreactive tissues in the model group were all significantly higher than those in control group(P<0.05); mean density of GABA immunoreactive tissues in themodel group were significantly lower than those in control group(P<0.05), meanwhile there were no differences between the two groups concerning the immunoreactive area and IOD(P>0.05); there were no differences between the two groups concerning the immunoreactive area, mean density and IOD of AchE and TH immunoreactive tissues (P>0.05).As to the posterior horn of spinal cord, immunoreactive area, mean density and IOD of SP and AchE immunoreactive tissues in the model group were all significantly higher than those in control group(P<0.05) and there were no differences between the two groups concerning the immunoreactive area, mean density, IOD of VIP, GABAand TH immunoreactive tissues (P> 0.05).As for the hypothalamus and the cingulate gyrus, immunoreactive area, mean density and IOD...
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