Selective inhibition of 5-HT7 receptor reduces CGRP release in an experimental model for migraine.
OBJECTIVE
To investigate the role of 5-HT(7) receptors on the release of calcitonin gene-related peptide (CGRP) in an animal model of migraine.


BACKGROUND
Calcitonin gene-related peptide has been identified as a key neuropeptide in the pathophysiology of migraine. It is elevated in the external jugular vein during migraine attacks in humans and after stimulation of the trigeminal ganglion in animal models of migraine. This can be treated with the 5-HT(1B/1D) receptor agonist sumatriptan concomitant with headache relief. Nevertheless, triptans, the most effective agents for the treatment of acute migraine attacks, are not effective in more than 1/3 of migraineurs and less than 50% of migraineurs achieve complete pain freedom. This indicates other serotonin receptors may be involved in the pathophysiology of migraine. Increasing evidence has shown that 5-HT(7) receptors may be involved in migraine pathogenesis. However, direct evidence for the role of 5-HT(7) receptors in migraine is still lacking.


METHODS
Unilateral electrical stimulation of the trigeminal ganglion (TGES) was performed in anesthetized male Sprague-Dawley rats. Animals were pretreated with sumatriptan (300 microg/kg, i.v.), selective 5-HT(7) receptor antagonist SB269970 (5, 10 mg/kg, s.c.), potential 5-HT(7) receptor agonist AS19 (5, 10 mg/kg, s.c.) or co-administration of SB269970 and AS19 (10 mg/kg, s.c.). Serum CGRP concentrations in the ipsilateral jugular vein were determined before and at 2 and 5 minutes after the start of TGES.


RESULTS
Our results showed that sumatriptan almost completely inhibited the release of CGRP evoked by TGES. Pre-administration of SB269970 (5, 10 mg/kg) caused a significant decrease in serum CGRP concentrations at 2 and 5 minutes following the onset of TGES, with a less inhibitory effect compared with sumatriptan. AS19 had no significant effect on CGRP release, while the SB269970-induced inhibitory effect was reversed by AS19.


CONCLUSIONS
Selective inhibition of 5-HT(7) receptors partly reduced CGRP release evoked by TGES. These findings suggest that 5-HT(7) receptors may play a role in the pathophysiology of migraine.
Department of Neurology, First Affiliated Hospital, Sun Yat-sen University, Guangzhou, Guangdong, China.
Xiaojuan
X
Wang
Yannan
Y
Fang
Jianbo
J
Liang
Zhao
Z
Yin
Jiayin
J
Miao
Ning
N
Luo
D000818:Animals; D015740:Calcitonin Gene-Related Peptide / Q000097:blood / Q000378:metabolism*; D004195:Disease Models, Animal; D004558:Electric Stimulation; D008297:Male; D008881:Migraine Disorders / Q000188:drug therapy / Q000378:metabolism* / Q000503:physiopathology; D009433:Neural Inhibition / Q000187:drug effects / Q000502:physiology; D009619:Nociceptors / Q000187:drug effects / Q000378:metabolism; D010636:Phenols / Q000494:pharmacology; D017729:Presynaptic Terminals / Q000187:drug effects / Q000378:metabolism; D011720:Pyrazoles / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D011985:Receptors, Serotonin / Q000187:drug effects / Q000378:metabolism*; D011984:Sensory Receptor Cells / Q000187:drug effects / Q000378:metabolism; D012702:Serotonin Antagonists / Q000494:pharmacology; D017366:Serotonin Receptor Agonists / Q000494:pharmacology; D013449:Sulfonamides / Q000494:pharmacology; D013764:Tetrahydronaphthalenes / Q000494:pharmacology; D012668:Trigeminal Ganglion / Q000187:drug effects / Q000378:metabolism / Q000503:physiopathology; D014276:Trigeminal Nerve / Q000187:drug effects / Q000378:metabolism* / Q000503:physiopathology; D014363:Tryptamines / Q000494:pharmacology
C505862:AS 19 compound; D010636:Phenols; D011720:Pyrazoles; D011985:Receptors, Serotonin; C404922:SB 269970; D012702:Serotonin Antagonists; D017366:Serotonin Receptor Agonists; D013449:Sulfonamides; D013764:Tetrahydronaphthalenes; D014363:Tryptamines; C104425:serotonin 7 receptor; D015740:Calcitonin Gene-Related Peptide