QUANTITATION OF N-TERMINALLY EXTENDED TACHYKININS IN CEREBROSPINAL-FLUID FROM HEALTHY-SUBJECTS

N-terminally extended substance P (SP) and neuropeptide K (NPK), an N- terminally extended form of neurokinin A (NKA), were determined in cer ebrospinal fluid (CSF) from healthy human subjects by combined high pe rformance liquid chromatography and radioimmunoassay. The concentratio ns of the peptides were similar in fresh CSF and in CSF which had been kept frozen for up to 5 months. SP and NKA were not present in measur able amounts in neither fresh CSF nor in CSF that had been frozen. On the other hand, when synthetic SP and NKA were added to approx. 2 pM c oncentration to fresh CSF samples, both peptides were recovered to 85 and 98%, respectively. There were no significant concentration gradien ts of the peptides in the first 18 ml (three consecutive 6 ml fraction s) of CSF (n = 10). In contrast, we confirmed previous findings, that there are gradients of the amine metabolites 5-HIAA (P < 0.01) and HVA (P < 0.001) (n = 5). The concentrations of extended SP (expressed in SP equivalents) and NPK in the first 6 ml of CSF were 1.5 +/- 0.7 pM a nd 14.2 +/- 6.4 pM (mean +/- S.D., n = 10), respectively. The present results thus show that the levels of N-terminally extended SP and NKA are stable in frozen CSF samples for up to 5 months. The virtual lack of SP and NKA in CSF does not seem to be due to losses during sample p reparation or storage.