2. THE CGRP SYSTEM and MIGRAINE.
CGRP and its receptor are extensively expressed in two separate neuron
populations in the TGV system (Eftekhari, Salvatore, Calamari, Kane,
Tajti & Edvinsson, 2010). CGRP is released from the TGV system in
conjunction of acute attacks of migraine and cluster headache (Ho,
Edvinsson & Goadsby, 2010). The trigeminal C-fibres and ganglia are the
main source of stimulus-induced CGRP found in the jugular vein as shown
in man and cat (Goadsby, Edvinsson & Ekman, 1988) and rat (Hoffmann,
Wecker, Neeb, Dirnagl & Reuter, 2012). The C-fibres have both afferent
and efferent aspects; perivascular fibres release CGRP onto the vascular
smooth muscle cells to induce dilatation and on dural mast cells to
participate in induction of neurogenic inflammation (Pietrobon &
Moskowitz, 2013). Many outstanding questions remain, particularly
regarding the other members of the CGRP family. This group of signalling
peptides include calcitonin (CT), adrenomedullin (AM) and amylin (AMY)
and their receptors (Table 1). A fair question is often asked: Can other
peptides be released in the TGV and will CGRP acting drugs have effects
that include other related receptor targets?