Treatment of Crohns disease(CD)and ulcerative colitis(UC),collectively known as inflammatory bowel diseases(IBD),has been a major clinical challenge,whereas the incidence of IBD has been on the rise in China.Serotonin(ie,5-HT)released from enterochromaffin(EC)cells has recently been shown to promote mucosal immune and inflammatory reaction.In this short talk,I will present our recent experimental data that support the hyperpolarization-activated cyclic nucleotide-gated cation channels(HCNs)as important regulators of EC cell function.