Neuropeptide Y- and vasoactive intestinal polypeptide-containing nerve fibers in the human cerebral arteries: characteristics of distribution.

Perivascular innervation in cerebral arteries from 28 human fetuses at twelve to twenty-eight weeks' gestational age was studied histochemically. Neuropeptide Y (NPY)- and vasoactive intestinal polypeptide (VIP)- containing nerve fibers were densely distributed along with adrenergic and cholinergic nerve fibers in the major pial arteries at the base of the brain, an area that forms the circle of Willis, and in the lenticulostriate arteries. In contrast, distribution was sparse in the cortical circumflex branches of the middle cerebral artery, as compared with findings in the lenticulostriate artery of the same diameter. Densely distributed perivascular nerve fibers in the lenticulostriate arteries may play an important role in the pathogenesis of intracerebral hemorrhage.