Neurohypophysial hormones in cerebrospinal fluid of adults: absence of arginine vasotocin and of a diurnal rhythm of arginine vasopressin.

We previously reported a prominent diurnal rhythm of oxytocin (OT) in human cerebrospinal fluid (CSF) similar to the brisk CSF OT rhythm in monkeys. An OT CSF rhythm has not been found in lower species. In contrast, a pronounced arginine vasopressin (AVP) rhythm has been found in lower species, but the AVP CSF rhythm is less marked in subhuman primates. In patients (n = 7) in whom lumbar drains had been temporarily placed for treatment of CSF rhinorrhea, we obtained CSF samples every 6 h. In 6 of these 7 patients, we previously reported (1) finding a prominent CSF OT rhythm, with a peak at 1200 h, by analysis of variance of repeated measures. When the samples of CSF of these same 6 patients (plus 1 additional patient) were assayed for AVP, no AVP rhythm was found. We also measured AVP, OT, and arginine vasotocin (AVT) by RIA in single samples of CSF obtained from 23 other patients. In these single samples of CSF, mean AVP was 0.9 +/- 0.11 (+/- SEM) pg/ml, and OT was 3.7 +/- 0.5 microU/ml. CSF AVT immunoreactivity was 0.6 pg/ml or less in the 23 patients. Two pools of CSF were separated by reverse phase high pressure liquid chromatography. The peak OT and AVP, as determined by RIA, coeluted exactly with synthetic and human posterior pituitary OT and AVP, respectively. No immunoreactive AVT was found in the position of synthetic AVT in the eluates. Thus, OT and AVP are present in human adult CSF, but AVT is not. The lack of a prominent rhythm of AVP in human CSF is in marked contrast to the brisk OT rhythm. The rhythm of neurohypophysial peptides in human and subhuman primates is different from the rhythm in lower species, suggesting different functions for OT and AVP in the central nervous system of various species.