The effects of 5-HT1A, 5-HT1B and 5-HT1D receptor agonists on trigeminal nociceptive neurotransmission in anaesthetized rats

Pre-clinical studies have suggested that one mechanism of antimigraine action of the `triptan' 5-HT 1B/1D receptor agonists may be through inhibition of central nociceptive transmission in the trigeminal dorsal horn. In anaesthetized rats, the 5-HT 1B/1D receptor agonist, zolmitriptan (up to 3 mg kg −1 , i.v.), inhibited the action potential discharge of single trigeminal neurones to noxious electrical stimulation of the middle meningeal artery. In contrast, the selective 5-HT 1B receptor agonist, CP-93,129 (3-(1,2,5,6-tetrahydropyrid-4-yl)pyrrolo[3,2- b ]pyrid-5-one), and the 5-HT 1A receptor selective agonist 8-hydroxy-2-(di- n -propylamino)-tetralin (8-OH-DPAT) had no effect in this assay at up to 3 mg kg −1 , i.v.. Brain penetrant, triptan 5-HT 1B/1D receptor agonists may therefore mediate their central trigeminal anti-nociceptive action in the rat via 5-HT 1D , but not 5-HT 1B or 5-HT 1A , receptors.