Perivascular innervation of the cerebral circulation: involvement in the pathophysiology of subarachnoid hemorrhage.

The authors describe the perivascular innervation of cerebral circulation. The different nerve fiber systems can be classified as follows: 1. Sympathetic (noradrenaline, neuropeptide Y), 2. Parasympathetic (acetylcholine, vasoactive intestinal peptide/peptide histidine isoleucine (methionine), 3. Sensory (tachykinins, calcitonin gene-related peptide). Each of these systems is outlined by their basic anatomical and physiological facts. Then, the etiology of cerebral vasospasm after subarachnoid hemorrhage is discussed in relation to the cerebrovascular innervation.