[Role of the spinal serotoninergic, noradrenergic and dopaminergic systems in the mechanism of analgesia].

The aminergic systems arising from the supraspinal structures which innervate the spinal cord are involved in the control of the activity of 1) the sensory neurons 2) the motor neurons 3) at the thoracic level the neurons of vegetative system. During the last two decades numerous publications have been devoted to the study of the role of the serotonergic and the noradrenergic systems. Several groups have also identified a spinal dopaminergic innervation arising from supraspinal structures and suggested that this innervation is, like the two other systems, involved in those controls. All these studies have more particularly suggested that the serotonergic, noradrenergic and dopaminergic fibers which innervate the dorsal horn of the spinal cord play an important role in the control of the transmission of the nociceptive messages and are implicated in the mechanisms of analgesia. Data supporting this hypothesis are reported in the present paper. The criticisms which have been expressed about the hypothesis related to the role of the serotonergic system will be also presented.