Abstract: Objective To investigate the changes of excitatory and inhibitory neurons in submucosal plexus (SMP) of colon in a rat model of IBS-C. Methods The rat model of IBS-C was established by intragastric perfusion with icy water. Whole-thickness colon specimens were collected to prepare submucosal layer with intact SMP. Multiple immunofluorescence staining technique was used for detecting the total numbers of SMP neurons and ganglia, the numbers of the SMP neurons expressing specific neurochemical markers (ChAT, VIP, NOS), and the activation status of SMP neurons. Results Compared with control group, the intestinal transmission rate of model rats was slower, and the number of fecal granules and water content of feces were less than that of controls. In the colon SMP of rat with IBS-C( n=7), the total number of SMP neurons/HPF and the total number of activated neuron/HPF increased significantly（P<0.05）; the percentages of activated ChAT-IR neurons and activated VIP-IR neurons decreased significantly, and the percentage of activated NOS-IR neurons increased significantly. Conclusions The changes of colonic SMP may play an important role in the pathogenesis of IBS-C.

Key words: irritable bowel syndrome, enteric nervous system, submucosal neuron