Measurement of endorphins in human cerebrospinal fluid.Comparative study of various groups of patients

Abstract

Endorphin levels in human cerebrospinal fluid (CSF) have been determined by using the electrically stimulated mouse vas deferens bioassay.Endorphins were extracted by adsorption to a synthetic resin of Amberlite XAD-2 eluted with methanol, and dried under a nitrogen atmosphere.Three different groups of patients have been studied: a) control subjects without a history of pain (n = 25), b) patients with acute postoperative pain after high abdominal and thoracic surgery (n = 8) and c) patients with chronic pain due to discal hernia (n = 14).The endorphin levels (expressed as equivalents of Met-E) obtained from the control group were 4.36 +/- 0.7 pmol/ml.In the postoperative group an endorphin decrease of 0.42 +/- 0.07 pmol/ml, was found while in the chronic pain group the levels obtained were 1.39 +/- 0.2 pml/ml.Thus a significantly low level of CSF endorphins was observed in both the postoperative and the chronic pain group as compared with the controls (p less than 0.01).These results suggest a correlation between pain levels and endorphin concentration in CSF.However in the acute postoperative pain group other factors such as depletion of endorphins by drugs used for anesthesia or due to surgical stress cannot be excluded.