5‐HT1B receptors mediate potent contractile responses to 5‐HT in rat caudal artery

Abstract

5-Hydroxytryptamine (5-HT) evoked potent contractile responses in phenoxybenzamine-treated ring segments of rat caudal artery, partially contracted with U46619. Responses were mimicked by 5-HT₁-selective agonists with the potency order: RU24969 > 5-carboxamidotryptamine > 5-HT = CP 93,129 > > sumatriptan. 8-Hydroxy-N,N-dipropylaminotetralin was virtually inactive. Responses were unaffected by spiperone (0.1 μm) and mesulergine (1.0 μm), but were antagonized competitively by (±)-cyanopindolol affording agonist-independent pK_B estimates of 8.4 to 8.9. The pharmacological profile of this receptor is consistent with that of the 5-HT_1B subtype. Since the 5-HT_1B receptor is the rodent homologue of the 5-HT_1Dβ subtype, it might be anticipated that 5-HT_1Dβ receptors will be found to mediate vasoconstrictor responses in non-rodent species.