2.2. Visceral Hypersensitivity Model Establishment

Using the complete randomization method, the 8-day-old neonatal rats were divided into the normal control group and the model group. Neonatal rats in the normal control group received only genital scratching without other stimuli. For neonatal rats in the model group, we used the internationally recognized colorectal irritation method to prepare the IBS model [18]. Colorectal irritation was performed in awake animals. During the operation, liquid paraffin was applied to the surface of each balloon. The balloon was gently inserted anally along the physiological curvature of the rectum to the descending colon. At this point, the balloon was inflated at a pressure of 60 mmHg for 1 min. The injector was slowly withdrawn, and the balloon was removed. After 30 minutes, the same stimulation was repeated. Balloon stimulation was performed once every day at a fixed time for 14 days. Rats were continuously fed until the sixth week, when experimental grouping and processing were performed.