CALCITONIN-GENE-RELATED PEPTIDE (HUMAN ALPHA-CGRP) COUNTERACTS VASOCONSTRICTION IN HUMAN SUBARACHNOID HEMORRHAGE

Calcitonin gene-related peptide (CGRP) is a neuropeptide co-stored wit h tachykinins (substance P, neurokinin A) in cerebrovascular sensory f ibers in the trigeminal ganglion. Preceding studies on subarachnoid he morrhage (SAH) revealed that an enhanced release of CGRP resulted in t he selective loss of perivascular CGRP. Therefore, the present study w as designed to evaluate the effects of intravenous administration of h uman alpha-CGRP on cerebral vasoconstriction in the postoperative cour se after SAH in 5 patients (8 infusions). Cerebral vasoconstriction wa s evaluated with transcranial Doppler sonography. The increase in the relationship between middle cerebral artery (MCA) velocity and interna l carotid artery (ICA) velocity (the hemodynamic index) was used as an indicator of vasoconstriction and compared to the contralateral side. A significant reduction was found in the hemodynamic index during the CGRP infusion (4.3 +/- 0.5, P < 0.05) as to compared to before infusi on (6.2 +/- 0.5). There was no measurable change in the hemodynamic in dex on the contralateral side. No significant change was observed in p ulsatility index, blood pressure or consciousness during the peptide i nfusion. A significant increase in heart rate was observed during the infusion as compared to before and after infusion (90 +/- 4 vs. 76 +/- 5). Cardiac ultrasound data indicated a mean cardiac output increase of 1.9 liter/min, and a mean decrease in total peripheral resistance o f 538 dynes s/cm(5). The results obtained show that infusion of human alpha-CGRP may induce normalisation of cerebrovascular tone in SAH.