The impact of long-course chemoradiotherapy on the myenteric plexus, neuromuscular functions and responses to prokinetic drugs in the human rectum.

Several months after chemoradiotherapy, the rectum was not inflamed and myenteric neuron numbers/phenotype unchanged. However, nitrergic activity was increased relative to cholinergic activity, and prokinetic-like drug activity was lost or greatly reduced. Thus, chemoradiotherapy causes long-term changes in neuromuscular functions and markedly reduces the efficacy of drugs for treating constipation.