5-HT1-like receptor mediated changes in porcine carotid haemodynamics: are 5-HT1D receptors involved?
5-Hydroxytryptamine (5-HT) reduces porcine arteriovenous shunting in the carotid vascular bed by stimulation of both 5-HT1-like and 5-HT2 receptors and increases capillary flow to some tissues, like the skin and ears, by different 5-HT1-like receptors. In view of the heterogeneous nature of the 5-HT1-like receptors and the relative selectivity for the 5-HT1D binding sites of sumatriptan, which also reduces porcine arteriovenous shunting and slightly increases capillary blood flow towards skin and ears by 5-HT1-like receptors, we have attempted to determine whether one or both of these carotid 5-HT1-like receptors belong to the 5-HT1D subtype. Pentobarbitone anaesthetized pigs, subjected to bilateral cervical vagosympathectomy, received either 5-HT (2 micrograms.kg-1.min-1) in the carotid artery or cumulative i.v. doses of sumatriptan (10, 30, 100 and 300 micrograms.kg-1). Their effect on the total carotid blood flow and its distribution into capillary and arteriovenous anastomotic parts was determined with radioactive microspheres. The effect of metergoline (1 mg.kg-1), a substance with a very high affinity for the 5-HT1D receptor as well as for the 5-HT1A, 5-HT1B, 5-HT1C and 5-HT2 receptors, was studied on the responses to 5-HT and sumatriptan. Both 5-HT and sumatriptan reduced carotid arteriovenous anastomotic blood flow. 5-HT and, to a lesser extent, sumatriptan also increased capillary blood flow towards some tissues. Metergoline by itself did not affect the distribution of porcine carotid blood flow.(ABSTRACT TRUNCATED AT 250 WORDS)
Den Boer
M O
MO
Department of Pharmacology, Faculty of Medicine and Health Sciences, Erasmus University, Rotterdam, The Netherlands.
Villalón
C M
CM
Saxena
P R
PR
D000818:Animals; D002339:Carotid Arteries / Q000187:drug effects / Q000502:physiology*; D006439:Hemodynamics / Q000187:drug effects / Q000502:physiology*; D007211:Indoles / Q000494:pharmacology; D011985:Receptors, Serotonin / Q000187:drug effects / Q000502:physiology*; D012039:Regional Blood Flow / Q000187:drug effects; D012701:Serotonin / Q000494:pharmacology; D013449:Sulfonamides / Q000494:pharmacology; D018170:Sumatriptan; D013552:Swine
D007211:Indoles; D011985:Receptors, Serotonin; D013449:Sulfonamides; D012701:Serotonin; D018170:Sumatriptan