Characterization of 5-HT receptors mediating constriction of porcine carotid arteriovenous anastomoses; involvement of 5-HT1B/1D and novel receptors.
1. It was previously shown that porcine cranial arteriovenous anastomoses (AVAs) constrict to 5-hydroxytryptamine (5-HT), ergotamine, dihydroergotamine, as well as sumatriptan and that sumatriptan acts exclusively via 5-HT1B/1D receptors. The present study was devoted to establish the contribution of 5-HT1B/1D receptors in the constriction of AVAs elicited by 5-HT (in presence of 0.5 mg kg(-1) ketanserin), ergotamine and dihydroergotamine in anaesthetized pigs. 2. Intracarotid infusion of 5-HT (2 microg kg(-1) min(-1)) and intravenous doses of ergotamine (2.5-20 microg kg(-1)) and dihydroergotamine (3-100 microg kg(-1)) reduced AVA and increased nutrient blood flows and vascular conductances. The vasodilator response to 5-HT, observed mainly in the skin and ear, was much more prominent than that of the ergot alkaloids. 3. Treatment with the 5-HT1B/1D receptor antagonist GR127935 (0.5 mg kg(-1), i.v.) significantly attenuated both ergot-induced AVA constriction and arteriolar dilatation, whereas GR127935 only slightly affected the carotid vascular effects of 5-HT. 4. The results suggest that 5-HT constricts carotid AVAs primarily via receptors, which seem to differ from those (5-HT1B/1D) stimulated by sumatriptan. The ergot alkaloids produce AVA constriction for a substantial part via 5-HT1B/1D receptors, but also stimulate unidentified receptors. Both these non-5-HT1B/1D receptors may be targets for the development of novel antimigraine drugs. 5. The moderate vasodilator response to the ergot derivatives seems to be mediated, at least in part, by 5-HT1B/1D receptors, whereas the arteriolar dilatation caused by 5-HT may be mediated by other, possibly 5-HT7 receptors.
De Vries
P
P
Department of Pharmacology, Faculty of Medicine and Health Sciences, Erasmus University Rotterdam, The Netherlands.
Villalón
C M
CM
Heiligers
J P
JP
Saxena
P R
PR
D000818:Animals; D001163:Arteriovenous Anastomosis / Q000502:physiology*; D002339:Carotid Arteries / Q000502:physiology*; D004876:Ergot Alkaloids / Q000494:pharmacology; D006439:Hemodynamics / Q000187:drug effects; D007650:Ketanserin / Q000494:pharmacology; D010069:Oxadiazoles / Q000494:pharmacology; D010100:Oxygen / Q000097:blood; D010879:Piperazines / Q000494:pharmacology; D011985:Receptors, Serotonin / Q000187:drug effects / Q000502:physiology*; D012701:Serotonin / Q000494:pharmacology; D012702:Serotonin Antagonists / Q000494:pharmacology; D013552:Swine; D014661:Vasoconstriction / Q000187:drug effects
D004876:Ergot Alkaloids; D010069:Oxadiazoles; D010879:Piperazines; D011985:Receptors, Serotonin; D012702:Serotonin Antagonists; C090701:GR 127935; D012701:Serotonin; D007650:Ketanserin; D010100:Oxygen