Co-localization of 5-HT_IB/ID/IF receptors and glutamate in trigeminal ganglia in rats

Anti-migraine triptan drugs are 5-HT_IB/ID receptor agonists which are thought to block the neurotransmitter/neuropeptide release from sensory nerve terminals and directly constrict blood vessel smooth muscles. In the present study, we have investigated the anatomical basis for a possible modulation of glutamate release from trigeminal ganglion neurons by 5-HT_IB/ID receptor agonists and by 5-HT_IF receptor agonists, using double immunohistochemical staining technique in the rat. The majority of 5-HT_IB, 5-HT_ID or 5-HT_IF receptor positive neurons were also glutamate positive, but both 5-HT_IB, 5-HT_ID or 5-HT_IF receptor single-labeled and glutamate single-labeled neurons were observed. These results suggest that 5-HT_IB/ID/IF receptor agonists may modulate glutamate release, and that one mechanism of their anti-migraine action could be the blockade of glutamate release.