[Stimulation of the periaqueductal gray matter for pain : electrical activity and evoked potentials (author's transl)].

There is some evidence that stimulation of the periaqueductal gray matter produced analgesia is accomplished by the activation of neuronal systems where endorphins are thought to be transmittors. However, the neurophysiological mechanism of this stimulation is not elucided. In this preliminary paper, the spontaneous and the evoked electrical activity has been studied in 3 patients operated on with implantation of an electrode in the periaqueductal gray matter for chronic pain. Particularly interesting are the pronounced decrease of the evoked potentials in the sensory nucleus of the thalamus after stimulation of the periaqueductal gray matter.