Enkephalin-like material in normal human CSF: measurement and levels

An opioid material in normal human lumbar CSF has been partially characterized and quantified. This material resembles methionine-enkephalin in its behavior in two chromatographic systems. It interacts with the opiate receptor assay and with a methionine-enkephalin radioimmunoassay. Mean human values are 3.12–3.25 pmoles of methionine-enkaphalin equivalents but the median is 1.7–1.9 pmoles. While this material resembles enkephalin, it cannot be identified as such with our current techniques.