Calcitonin gene-related peptide-LI in subarachnoid haemorrhage in man. Signs of activation of the trigemino-cerebrovascular system?

Calcitonin gene-related peptide (CGRP) is a neurotransmitter candidate together with the tachykinins in sensory fibres in the cerebral vasculature, with possible vasodilating properties. The origin of most of the CGRP-immunoreactive cerebrovascular nerve fibres seems to be the trigeminal ganglion. Experimentally produced vasoconstriction in cats after lesions of the trigeminal ganglion have shown marked prolonged constriction compared to controls. The possible involvement of the trigemino-cerebrovascular system as a defence system, with CGRP probably being the more potent vasodilatator, was investigated in 12 patients with subarachnoid haemorrhage (SAH). After operation with clipping of the aneurysm and treatment according to department policy, blood samples were taken from the external jugular vein on postoperative days 1, 2, 3, 5, 7, 9, frozen and analysed (radioimmunoassay) for CGRP-LI (-like immunoreactivity) levels. The patients were monitored with Doppler recordings from the middle cerebral arteries (MCA) and internal carotid arteries (ICA) following blood sampling. The relationship Vmean MCA/V mean ICA was used as an index of vasospasm. The highest CGRP-LI levels were found in the patient with highest velocities/index values. In patients with MCA aneurysms (n = 7), a correlation of r = 0.61 was found between the index and CGRP-LI levels. However, significant changes in the group as a whole was not found. The possible involvement of the trigemino-cerebrovascular system in SAH is discussed.