Perivascular nerves with immunoreactivity to vasoactive intestinal polypeptide in cephalic arteries of the cat: Distribution, possible origins and functional implications
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Abstract
The distribution of nerves containing vasoactive intestinal polypeptide(VIP)-immunoreactive
material was examined in the cephalic arteries and cranial nerves of cats using an
indirect immunofluorescence procedure on whole mounts. Perivascular VIP-immunoreactive
nerves were widely distributed in arteries and arterioles supplying glands, muscles
and mucous membranes of the face. Within the cerebral circulation, perivascular VIP-immunoreactive
nerves were most abundant in the circle of Willis and the proximal portions of the
major cerebral arteries and their proximal branches supplying the rostral brainstem
and ventral areas of the cerebral cortex. Nerves containing VIP-immunoreactive material
were absent from distal portions of arteries supplying the posterior brainstem, cerebellum
and dorsal cerebral cortex. Cerebral perivascular VIP-immunoreactive nerves had extracerebral
origins probably from VIP-immunoreactive perikarya within microganglia in the cavernous
plexus and external rete. Extracerebral perivascular VIP-immunoreactive nerves probably
arose from VIP-immunoreactive perikarya in microganglia associated with the tympanic
plexus, chorda tympani, lingual nerve and Vidian nerve as well as from cells in the
otic, sphenopalatine, submandibular and sublingual ganglia. Therefore, it seems likely
that each major segment of the cephalic circulation is supplied by local VIP-immunoreactive
neurons. If the VIP-immunoreactive nerves cause vasodilation, they are well placed
to allow redistribution of arterial blood flow within the head. During heat stress,
neurogenic vasodilation of the appropriate beds would permit efficient cooling of
cerebral blood, particularly that supplying the rostral brainstem and surrounding
areas of the cerebral cortex.