Possible neurohumoral mechanisms in CNS stimulation for pain suppression.

Improved knowledge about biochemical mechanisms underlying pain suppression by CNS electric stimulation is one condition for the further advancement of this form of treatment. In 6 patients treated with PVG stimulation and in 14 with spinal cord stimulation the concentration of substance P-like immunoreactivity in lumbar CSF increased significantly following stimulation. However, these changes may be unspecific and not directly related to the suppression of pain. Measurements of somatostatin, cholecystokinin, vasoactive intestinal polypeptide, neurotensin and monoamine metabolites in CSF showed no changes related to stimulation and the ensuing pain relief. Possible reasons for these negative findings are discussed.