CSF NEUROPEPTIDES IN CANCER PAIN - EFFECTS OF SPINAL OPIOID THERAPY

The cerebrospinal fluid (CSF) levels of the opioid peptides met-enkeph alin (ME), beta-endorphin (BE) and dynorphin (DYN) as well as the puta tive sensory neuropeptides substance P (SP), somatostatin (SOM), calci tonin gene related peptide (CGRP) and vasoactive intestinal polypeptid e (VIP) were determined in 10 patients with severe nociceptive pain du e to malignancy, before and after initiation of spinal opioid therapy, and in 10 control patients. Pain intensity, evaluated by means of a 1 00-mm visual analog scale (VAS), was reduced from 39 +/- 9 to 18 +/- 1 0 for continuous pain and from 70 +/- 10 to 10 +/- 8 for intermittent pain (means +/- s.e.mean). Lumbar CSF immunoreactive ME and DYN concen trations were significantly increased (P = 0.05) and BE and VIP were s ignificantly decreased (P less-than-or-equal-to 0.05) in the pain pati ents. A slight, but non-significant (P = 0.06) decrease in SP-like imm unoreactivity was found after initiation of spinal opioid therapy. Vis ceral pain seemed to be associated with low immunoreactive SP and ME c oncentrations compared to somatic pain. A highly significant correlati on was found between SP and ME (P < 0.001) and to a lesser extent also between other peptides. We conclude that the concentrations of the en dogenous opioids were more affected by nociceptive pain states than th e non-opioid peptides. The origin of pain may also influence the resul ts. The postulated inhibition of peptide release by spinal opioid appl ication seemed to be present for SP, but could otherwise not be confir med.