Hypothalamic neuropeptide release after experimental subarachnoid hemorrhage: in vivo microdialysis study

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Abstract
Objectives – As evidence exists about independent regulation of peripheral and central release of the vasoactive and natriuretic neuropeptides arginine–vasopressin (AVP) and oxytocin (OXT), we investigated their release patterns following subarachnoid hemorrhage (SAH). Materials and methods – After injection of 0.1 ml arterial blood or saline into the great cistern of 33 Wistar rats, AVP and OXT levels were measured in blood and by microdialysis in the hypothalamic supraoptic (SON) and paraventricular nucleus (PVN). For statistical analysis, the analysis of variance (ANOVA) was used with Tukey HSD post hoc ANOVA tests to determine specific group differences. Results – Plasma AVP and OXT peaked 2 h after SAH (P < 0.05), and normalized at 4 h. In the SON, both AVP and OXT peaked 4 h after SAH (P < 0.05). In the PVN, AVP increased in both groups (P < 0.05), while no OXT release occurred. By the sham group, any effect of experimental procedure was excluded. Conclusions – The SAH‐specific central neuropeptide release, which exceeded peripheral release and continued longer, may contribute to pathophysiological events following SAH.