[Analgesia: role of the brainstem (author's transl)].

Potent analgesia results from electrical stimulation of the periaqueductal grey matter in several species including man. Electrophysiological experiments indicate that this electrical analgesia could result from the activation of descending influences which inhibit the activity of dorsal horn interneurons in the transmission of painful messages. Numerous physiological, behavioral and pharmacological studies mention that the descending serotoninergic Bulbo-spinal system plays a major role in electrical analgesia. Several studies suggest that both electrical and morphine analgesia share, at least in part, a common site and mechanism of action. This possibility is mainly supported by the fact that analgesia induced by electrical stimulation is suppressed or reduced by a specific opiate antagonist (Naloxone).