Determination of beta-endorphin and substance P in small volumes of human cerebrospinal fluid.

A reversed-phase high-performance liquid chromatography procedure combined with radioimmunoassay (rp-HPLC-RIA) is presented. It makes possible the quantitative determination of the neuropeptides, beta h-endorphin and substance P, in small volumes of cerebrospinal fluid (CSF). The concentration-dependence of the recovery of the method is demonstrated and the effect of free silanol groups of the stationary phase on the recovery is discussed. CSF was shown to contain 9.6 +/- 1.1 fmol beta h-endorphin and 12.0 +/- 0.9 fmol substance P per ml.