Peptide‐containing nerve fibers in human cerebral arteries: Immunocytochemistry, radioimmunoassay and in vitro pharmacology

Abstract

Nerve fibers containing neuropeptide Y, vasoactive intestinal peptide (VIP), substance P (SP), and calcitonin generelated peptide (CGRP) were seen in the adventitia or at the adventitia–media border of human cerebral arteries obtained during neurosurgical procedures Radioimmunoassay of human cerebral arteries, removed at autopsy, revealed that the levels of the four peptides did not differ among the major cerebral arteries. There was, however, a gradual decline in peptide concentrations with increasing age of the patients, as measured in the proximal part of the middle cerebral artery. Pharmacological experiments on fresh segments of cerebral (pial) arteries in vitro revealed that neuropeptide Y caused vasoconstriction per se but did not potentiate the contractile response of noradrenaline. VIP, peptide histidine methionine-27 (PHM-27), SP, neurokinin A (NKA), and human CGRP potently relaxed vessels precontracted by prostaglandin F_2α, the relative potency being human CGRP ≥ SP ≥ VIP ≥ NKA ≥ PHM-27. The amount of relaxation varied between 55% (SP) and 96% (human CGRP) of the prostaglandin F_2α–induced contraction. The peptide effects were not antagonized by propranolol, atropine, or cimetidine, suggesting an action that does not involve adrenergic, cholinergic, or histaminergic receptors.