Epidural injection of 2-4mg morphine for 7-14 days were given to 18 patients with severe chronic pain. All cases except 2 arachnoiditis had considerable amelioration of pain, which commenced within 2-3min, reached a peak in 10-20min, and was effective for 6-72 hours. Using sensory evoked potentials(SEP) examination for pre-and post-morphine epidural infusion in 18 pain patients, we found the morphine inhibited the action of spinal pain receptor system. It is suggested that morphine reached the subarachnoid space and produced its effect by direct action on the specific opiate receptors in the substantia gelatinosa of the posterior horn cell of the spinal cord.
Arachnoid ; Arachnoiditis ; Chronic Pain* ; Humans ; Injections, Epidural ; Morphine* ; Nociceptors ; Posterior Horn Cells ; Receptors, Opioid ; Spinal Cord ; Subarachnoid Space ; Substantia Gelatinosa