[Intestinal sensitivity disorders and irritable bowel syndrome]

Long neglected in the past, the study of visceral sensitivity (interoception) has progressed in recent years because of advances in neurobiological techniques. Dealing with the structure or the function of single neurons, these techniques have profoundly increased our knowledge about the sensitive mechanisms in the digestive tract. According to recent data, the visceral sensitivity organs are richer and more complex than imagined previously. Microphysiological techniques have shown that intestinal sensitive terminations are capable of transmitting information concerning visceral activity and physicochemical modifications of intestinal contents directly to the central nervous system. This means that visceral sensitivity intervenes under physiological as well as pathological conditions. This notion is new and of great interest. As progress was being made concerning the morphologic and electrophysiologic aspects and contemporaneous studies were establishing the richness of visceral, and particularly, intestinal, sensitive receptors, basic science research in humans and animals have emphasized the diversity of the implication of the extrinsic nervous system in pain, regulation of digestive motility, homeostasis and alimentary behaviour. Our present knowledge on the nervous and neurohumoral mechanisms has shed new light on the determinisms in digestive tract pathology. This is especially true in the irritable bowel syndrome which can be considered as an extrinsic nervous system derangement. Due to abnormal sensitivity by modification of the threshold values of sensitivity to distension, and/or to stimulation by substances such as cholecystokinin, for example, motor disorders occur. Other factors, such as stress, can be responsible for revelation or exacerbation of neurohumoral disorders.