Irritable bowel syndrome: a model of the brain-gut interactions.

Brain-gut interactions are increasingly recognized as underlying pathomechanisms of functional gastrointestinal disorders. Bi-directional communication between the central nervous system (CNS) and the enteric nervous system (ENS) occurs both in health and disease. Various CNS- and gut-directed stressors stimulate the brain-gut axis. Processes modulating responsiveness to stressors along the brain-gut axis involve neural pathways, the immunological, and endocrinological mechanisms. Disturbances at every level of neural control of the gastrointestinal tract can affect modulation of gastrointestinal motility, secretion, immune functions as well as perception and emotional response to visceral events. ENS function, central processing, and autonomic regulation play an important role in the brain-gut dialogue. Stress and emotions may trigger neuroimmune and neuroendocrine reactions via the brain-gut axis. Various non-site specific neurotransmitters influence gastrointestinal, endocrine and immune function, as well as human behavior and emotional state, depending on their location. The physiology of the digestive tract, the subjective experience of symptom, health behavior, and treatment outcome are strongly affected by psychosocial factors. Recently, a biopsychosocial model of IBS containing physiological, emotional, cognitive and behavioral components has been proposed. Rapid progress in neurogastroenterology, using new brain imaging techniques, should bring better understanding of the brain-gut axis and open new therapeutic perspectives.