Peptidergic innervation of the cerebral circulation. Role in subarachnoid hemorrhage in man

Abstract

The present paper reviews recent studies in monkey and man adding further to understanding of the role of perivascular peptides in the pathophysiology of subarachnoid haemorrhage. The perivascular fibers, sympathetic fibers (storing noradrenaline, neuropeptide Y), parasympathetic fibers (storing acetylcholine, vasoactive intestinal peptide, peptide histidine methionine and neuropeptide Y) and sensory fibers (storing tachykinins, calcitonin gene-related peptide) were traced using True Blue in monkey. Tracing studies of the monkey middle-cerebral artery (MCA) innervation confirmed earlier studies in rats and cats, with superior cervical and trigeminal ganglia as main immunostaining areas, and contralateral involvement in the superior cervical and trigeninal ganglia. Sphenopalatine immunostaining was scarce. The release of neuropeptides in the external jugular vein in humans in the postoperative course after subarachnoid hemorrhage, using radioimmunoassay, was correlated to hemodynamical changes (vasoconstriction) monitored with Doppler ultrasound on middle cerebral (MCA) and internal carotid arteries (ICA). Neuropeptide Y-like immunoreactivity (NPY-LI) levels were increased compared to controls in patients with hemodynamic changes, and in some patients a relationship was found between velocities and NPY-LI. Calcitonin gene-related peptide-LI levels were also increased in connection with vasospasm. In patients with MCA lesions a correlation of 0.61, p=0.0002 was found between hemodynamic index (V MCA/V ICA) and CGRP-LI. The possible sympathetic and trigemino-cerebrovascular activation are discussed.