BDNF and irritable bowel syndrome: After CKF treatment, the levels of 5-HT, 5-HT1A, PKA, CREB, and BDNF increased in the hippocampus and decreased in the colon, thereby indicating that CKF can alleviate the symptoms of IBS rats by modulating the brain-gut axis through the 5-HT1A-PKA-CREB-BDNF pathway.