5-HT receptors mediating contraction in the rat-tail artery.
We studied the effects of 5-HT in resistance vessels. Compounds acting on 5-HT2A and 5-HT1B receptors were tested on rat-tail arterial rings in varying experimental conditions. We tested 5-HT from 50 nM to 100 microM: the pD2 was 6.4 +/- 0.1. We evaluated vasoconstriction by 5-HT in tissues slightly depolarized with 30 mM KCl. In this condition, the 5-HT concentration-related contraction started at lower concentration in comparison to control tissues. Preincubation with 50 nM ketanserin, a 5-HT2A-antagonist, and 1 microM prazosin, an alpha1-antagonist, strongly inhibited concentration-related contraction by 5-HT: the pD2 was 3.2 +/- 0.2. Moreover, we experimented alpha-methyl-5-HT (alpha-me-5-HT) and 5-carboxamidotryptamine (5-CT), selective agonists at 5-HT2A and 5-HT1B receptors, respectively. Both agonists induced concentration-related contraction; the potency order observed was 5-HT > alpha-me-5-HT > 5-CT. Finally, we studied SB 224289, a selective 5-HT1B-antagonist, on contraction by 5-HT in control and in depolarized conditions. 0.2 microM SB 224289 significantly inhibited vasoconstriction induced by 5-HT in depolarized vascular tissues. The data indicate that vasoconstriction induced by 5-HT is mainly dependent on 5-HT2A receptors; however, 5-HT1B receptors are also present in rat-tail artery.
Froldi
Guglielmina
G
Department of Pharmacology and Anesthesiology, University of Padova, Largo E. Meneghetti 2, I-35131 Padova, Italy. g.froldi@unipd.it
Nicoletti
Patrizia
P
Caparrotta
Laura
L
Ragazzi
Eugenio
E
D000818:Animals; D001158:Arteries / Q000187:drug effects / Q000502:physiology; D007650:Ketanserin / Q000494:pharmacology; D008297:Male; D010881:Piperidones / Q000494:pharmacology; D011224:Prazosin / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D044302:Receptor, Serotonin, 5-HT1B / Q000187:drug effects / Q000502:physiology*; D044402:Receptor, Serotonin, 5-HT2A / Q000187:drug effects / Q000502:physiology*; D012701:Serotonin / Q000031:analogs & derivatives* / Q000494:pharmacology; D012702:Serotonin Antagonists / Q000494:pharmacology; D017366:Serotonin Receptor Agonists / Q000494:pharmacology; D013141:Spiro Compounds / Q000494:pharmacology; D014661:Vasoconstriction / Q000187:drug effects / Q000502:physiology*
D010881:Piperidones; D044302:Receptor, Serotonin, 5-HT1B; D044402:Receptor, Serotonin, 5-HT2A; C108518:SB 22489G; D012702:Serotonin Antagonists; D017366:Serotonin Receptor Agonists; D013141:Spiro Compounds; C042390:alpha-methylserotonin; D012701:Serotonin; C047087:5-carboxamidotryptamine; D007650:Ketanserin; D011224:Prazosin