Journal of Neuroscience, Vol 8, 2468-2476, Copyright © 1988 by Society for Neuroscience
Enrichment of a vasoactive neuropeptide (calcitonin gene related peptide) in the trigeminal sensory projection to the intracranial arteries
TP O'Connor and D van der Kooy
Department of Anatomy, University of Toronto, Ontario, Canada.
Trigeminal sensory innervation of cerebral vessels and the surrounding dura
is responsible for most intracranial head pain. Small-diameter fibers
containing substance P (Sub P) have been observed in the periadventitia
around feline cerebral blood vessels, and it has been suggested that these
fibers are the trigeminal substrate for vascular pain associated with
cluster and migraine headaches. Calcitonin gene related peptide (CGRP)
coexists with Sub P in some of these fibers and with some Sub P containing
neurons in the trigeminal ganglion. In addition, a population of trigeminal
neurons containing CGRP but not Sub P has been observed. We now report that
the population of trigeminal ganglion cells projecting to the cerebral
vasculature is enriched in CGRP-containing neurons, and especially in the
population of neurons containing CGRP and not Sub P. Using retrograde
tracing of fluorescent tracers combined with immunocytochemistry after
explant culture, we found approximately 32% of trigeminal ganglion cells
projecting to the cerebral vasculature contained CGRP. Approximately 18 and
17% of these cells contained Sub P and cholecystokinin (CCK), respectively.
The 32% of ganglion cells projecting to the cerebral vasculature that
contain CGRP stands in contrast to the 12% CGRP positive seen in the
population of ganglion cells projecting out to another target (the
forehead), and the 21 and 23% CGRP positive observed in the mandibular
branch and entire ganglion, respectively. Sub P and CCK are not enriched in
the trigeminal innervation of the vasculature compared with their presence
in cells throughout the ganglia.(ABSTRACT TRUNCATED AT 250 WORDS)
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