Peptidergic Innervation of the Cerebral Vasculature and its Functional Signfiicance

Abstract

In the last decade, the number of neurotransmitters which have been proposed to be associated with the cerebral vasculature has increased to approximately 20. However, the dominant factors primarily responsible for the dynamic regulation of cerebral blood flow have long been considered to be vasoactive products of cellular metabolism, with perivascular hydrogen ions, potassium ions and adenosine being the most favoured candidates. Many cerebrovascular investigators would ascribe only a minor, if any, role in the regulation of cerebral blood flow to neurotransmitters. In the last five years, new anatomical evidence has rekindled great interest in neurogenic cerebrovascular influences. Cerebral blood vessels are not only innervated by nerve fibres originating in sympathetic ganglia and cranial nerve ganglia but there is considerable anatomical evidence that intracerebral neurones gives rise to process, some of which form synaptic contacts with other cortical neurones, and others which are intimately associated with the cerebral vasculature. Such anatomical arrangements could provide a mechanism by which neuronal firing and thus energy generation could be linked to local blood flow directly by a neurotransmitter. (For detailed review of cerebrovascular innervation, see Edvinsson and McCulloch, 1987).