[Current data on pain pathways].

Abstract

1--The classical notion attributing the conduction of painful messages to only the A delta and C fibres will be discussed. 2--Spinal cord cells of layers I, V and VIII received painful messages and their physiological properties will be compared. 3--The origin within the cell layers of the spinal cord of the various ascending bundles will be examined. 4--The reticular an thalamic zones (posterior ventra nucleus, mid-line and intralaminar nuclei, GMme posterior group in particular) which receive painful messages have also been studied using activation provoked by pinching, pinprick, the injection of painful substances and stimulation of the dental pulp. The possible role of the different structures thereby brought into action and the limitation of these techniques will be discussed. 5--The existence of metameric controls and controls of central origin active at a spinal, reticular and thalamic level. The absence of inhibitory controls may be responsible for the development of abnormal painful sensations which accompany certain deafferentation procedures. The reestablishment of these controls with the aid of stimulation may result and often results in the improvement of these painful syndromes. 6--Section of the dorsal routes in the chronic animal (rat and cat) may represent an experimental model for deafferentation pain seen in man.