ALTERATIONS IN PERIVASCULAR DILATORY NEUROPEPTIDES (CGRP, SP, VIP) INTHE EXTERNAL JUGULAR-VEIN AND IN THE CEREBROSPINAL-FLUID FOLLOWING SUBARACHNOID HEMORRHAGE IN MAN

A possible involvement of perivascular vasodilatory neuropeptides in s ubarachnoid haemorrhage (SAH) has been evaluated in man by measuring t he levels of calcitonin gene related peptide (CGRP)-, substance P (SP) - and vasoactive intestinal peptide (VIP)-like immunoreactivity (LI) i n the cranial venous outflow and in CSF in 34 patients admitted to the hospital after an acute SAH. After operation with aneurysm clipping a nd nimodipine treatment, blood samples were taken from the external ju gular vein (EJV) or cerebrospinal fluid (CSF) and analysed for neurope ptide levels with specific radioimmuno assays (RIA) during the postope rative course. The degree of vasoconstriction in the patients was moni tored with Doppler ultrasound recordings bilaterally from the middle c erebral (MCA) and internal carotid arteries (ICA) following the EJV bl ood sampling every second day. The mean value of all CGRP-LI measureme nts in EJV during the entire course of SAH (n = 20) revealed a signifi cantly higher level as compared to controls. The highest CGRP-LI level s were found in patients with the highest velocity index values (vasos pasm). The relationship V mean MCA/V mean ICA was used as an index of vasoconstriction. In patients with MCA aneurysms (n = 10), a significa nt correlation (r = 0.65, p < 0.05) was found between the vasospasm in dex 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 infusi on test) did not alter the levels of the perivascular peptides in the EJV. In addition, CGRP-, SP-, VIP- and neuropeptide Y (NPY)-LI were an alysed in CSF in the post-operative course after subarachnoid haemorrh age (SAH) in 14 patients. The CSF VIP-LI was lower in SAH than in cont rol (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 pm ol/L) were observed. The results of this study are in support of our h ypothesis that there is an involvement of the sensory peptide CGRP in a dynamic reflex aimed at counterbalancing vasoconstriction in SAH.