ABSTRACT
The existence of two prototypes of normal and depressed subjects has been postulated according to their distal colon motility profiles: low-intestinal tone (IT) and high-IT subjects. Because low-IT normal subjects proved to have a higher mean noradrenaline plasma level than high-IT normals, labeled the first group hypersympathetic and the latter group hyposympathetic. Although the results obtained from the present study in high- and low-IT depressed patients showed many similarities with those obtained in normals, some important differences were observed. One of the most interesting findings emerging from research is the demonstration that diastolic blood pressure is reduced by clonidine in low-IT hypersympathetic but not in high-IT hyposympathetic depressed patients. This finding provides a valid physiological marker for differentiating between the depressive syndromes. A great deal of research has been carried out to establish adequate biological markers of depression. With regard to this, many attempts have been made to find neuroendocrine parameters as a guide to diagnosis and therapy of depression.
