Alterations in perivascular dilatory neuropeptides (CGRP, SP, VIP) in the external jugular vein and in the cerebrospinal fluid following subarachnoid haemorrhage in man

A possible involvement of perivascular vasodilatory neuropeptides in subarachnoid haemorrhage (SAH) has been evaluated in man by measuring the levels of calcitonin gene related peptide (CGRP)-, substance P (SP)- and vasoactive intestinal peptide (VIP)-like immunoreactivity (LI) in the cranial venous outflow and in CSF in 34 patients admitted to the hospital after an acute SAH. After operation with aneurysm clipping and nimodipine treatment, blood samples were taken from the external jugular vein (EJV) or cerebrospinal fluid (CSF) and analysed for neuropeptide levels with specific radioimmuno assays (RIA) during the postoperative course. The degree of vasoconstriction in the patients was monitored with Doppler ultrasound recordings bilaterally from the middle cerebral (MCA) and internal carotid arteries (ICA) following the EJV blood sampling every second day. The mean value of all CGRP-LI measurements in EJV during the entire course of SAH (n = 20) revealed a significantly higher level as compared to controls. The highest CGRP-LI levels were found in patients with the highest velocity index values (vasospasm). The relationship Vmean MCA/Vmean ICA was used as an index of vasoconstriction. In patients with MCA aneurysms (n = 10), a significant correlation (r = 0.65, p < 0.05) was found between the vasospasm index and CGRP-LI levels. There were no changes observed in the SP- and VIP-LI levels. Alterations in cerebrovascular tone induced by changing arterial CO2 tension or lowering of blood pressure (ketanserin infusion test) did not alter the levels of the perivascular peptides in the EJV. In addition, CGRP-, SP-, VIP- and neuropeptide Y (NPY)-LI were analysed in CSF in the post-operative course after subarachnoid haemorrhage (SAH) in 14 patients. The CSF VIP-LI was lower in SAH than in control (p < 0.05). The CGRP-LI level was measurable in SAH CSF but not in CSF of controls. In individual patients with marked vasoconstriction increased levels of CGRP-LI (up to 14 pmol/L) and NPY-LI (up to 232 pmol/L) were observed. The results of this study are in support of our hypothesis that there is an involvement of the sensory peptide CGRP in a dynamic reflex aimed at counterbalancing vasoconstriction in SAH.