Extracerebral Vessels Research Paper

Extracerebral vessels, located at the base and surface of the brain, are innervated by perivascular nerves originating from the superior cervical ganglion, responsible for the sympathetic innervation, the sphenopalatine and otic ganglia, mainly supplying parasympathetic nerves, as well as the trigeminal ganglion [59]. This extrinsic innervation is lost, when perforating arteries enter the brain. These parenchymal arterioles have unique properties compared to the microvasculature found in other organs; endothelial cells are wrapped around by specialized contractile cells, termed pericytes or Rouget cells [60], that are embedded in the basement membrane, separating it from the endothelial cells, and project a sheath around endothelial cells, where they communicate with the endothelium through either
The basal lamina of the cerebral microvasculature is in close connection to astrocytes and neurons that regulate the surrounding microcirculation, hence it is termed intrinsic innervation. Intrinsic afferents originate from subcortical neurons, such as the basal forebrain, the raphe nucleus, locus coreuleus or local cortical interneurons [63, 64]; however this type of innervation targets mainly astrocytes rather than parenchymal arterioles [63]. Common feature of both extrinsic- and intrinsic innervation is that nerve endings do not form classical synaptic junctions, but generally enrich the vessel wall, and their ability to directly modulate the vascular tone upon stimulation [59]. The main role of the sympathetic innervation, beside the direct effect of vasocontraction, is to modulate the upper limit of autoregulation towards higher pressure, thus protects the brain against high blood