The involvement of the neuropeptides oxytocin (OXT) and vasopressin (AVP) in human socio-emotional behaviours is attracting increasing attention. There is ample evidence for elevated plasma levels upon a wide variety of social and emotional stimuli and scenarios, ranging from romantic love via marital distress up to psychopathology, with cause versus consequence being largely unclear. The present study examined whether plasma levels of both OXT and AVP are reflective of central neuropeptide levels, as assumed to impact upon socio-emotional behaviours. Concomitant plasma and cerebrospinal fluid (CSF) samples were taken from 41 non-neurological and nonpsychiatric patients under basal conditions. Although OXT and AVP levels in the CSF exceeded those in plasma, there was no correlation between both compartments, clearly suggesting that plasma OXT and AVP do not predict central neuropeptide concentrations. Thus, the validity of plasma OXT and AVP as potential biomarkers of human behaviour needs further clarification.

In the converging fields of neuroendocrinology and behavioural neuroscience, the interaction between peripheral secretion and central release of oxytocin in humans has not yet been comprehensively assessed. As the human brain is not directly accessible and as the collection of human cerebrospinal fluid (CSF) usually requires invasive procedures, easier accessible compartments such as blood or saliva attract increasing attention. In this study, we prospectively determined oxytocin concentrations in the three compartments plasma, CSF and saliva of fifty critically ill patients with neurological and neurosurgical diseases. All samples per patient were collected concomitantly. Oxytocin was measured by a highly sensitive and specific radioimmunoassay. Strength of correlation was assessed by the Spearman rank correlation coefficient. Correlation analyses revealed modest to strong correlations for oxytocin between the saliva and CSF compartments while predominantly weak correlations were found between the CSF and plasma as well as between the plasma and saliva compartments. In conclusion, we demonstrated modest to strong correlations between the saliva and CSF compartment suggesting that saliva oxytocin may help to assess CSF oxytocin levels. In contrast, plasma oxytocin failed to correspond well with CSF oxytocin levels as predominantly weak correlations were found between the CSF and plasma as well as between the plasma and saliva compartments which are unlikely to have a biological relevance. Further research is needed to clarify to what extent saliva oxytocin may serve as a biomarker reflecting brain oxytocin activity. This article is protected by copyright. All rights reserved.

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Our data indicate that NPY is involved in the pathogenesis of SAH-related CV and ischemia. Neuropeptide Y represents an early and reliable biomarker for the prediction of CV and consecutive stroke due to aneurysmal SAH.