Immunohistochemical demonstration of APP (avian pancreatic polypeptide)-immunoreactive nerve fibres around cerebral blood vessels.

Nerve fibres containing immunoreactive avian pancreatic polypeptide (APP) were demonstrated in the wall of cerebral blood vessels from several species. Pial arteries of chicken, mouse, rat, guinea-pig, cat and dog had a dense supply of APP fibres while APP fibres were less numerous in rabbit, cow and monkey. The APP-immunoreactive fibres were more numerous in the rostral part of the circle of Willis than around more caudally located pial vessels. Immunoreactive fibres were also seen in the wall of pial vessels of the spinal cord, as shown in the cat. Extirpation of the superior cervical sympathetic ganglion was followed by a marked reduction in the number of APP-containing fibres on the ipsilateral side of the brain.